Seediscussions,stats,andauthorprofilesforthispublicationat:https://www.researchgate.net/publication/229992338

TaxonomicstudiesonthediatomgenusNaviculaBory.Naviculagrevilli(C.A.Ag.)HeibergandN.Comoides(Dillwyn)H.andM.Peragallo

ARTICLEinBOTANICALJOURNALOFTHELINNEANSOCIETY·JUNE2008

ImpactFactor:2.53·DOI:10.1111/j.1095-8339.1978.tb01502.x

CITATIONS

14

READS

57

1AUTHOR:

EileenJCox

NaturalHistoryMuseum,London

125PUBLICATIONS1,985CITATIONS

SEEPROFILE

Availablefrom:EileenJCox

Retrievedon:03February2016

Botanical Journal of the Linnean Society, 76: 127-143. With 23 figures

February 1978

Taxonomic studies on the diatom genus Nuviculu Bory. NuvicuZa grevillii (C.A.Ag.) Heiberg and N . comoides (Dillwyn) H. & M. Peragallo EILEEN J. COX*

Department of Botany, University of Bristol, Woodland Road, Bristol BS8 1 UG

AND

Culture Centre of Algae and Protozoa, 36 Storey’s Way, Cambridge CB3 ODT

Accepted for publication January 1978

Two closely related species of the diatom genus Nauicuh were investigated using light and electron microscopy. A hitherto unrecorded structure associated with the raphe of N. delognei Van Heurck is described.

Examination of type material revealed that the nomenclatural types of N. greuillii (C.A.Ag.) Heiberg and N . comoides (Dillwyn) H. & M. Peragallo do not agree with the present understanding of these species, therefore alternative names were sought. All the synonyms of each species were traced and a table of synonymy is supplied. The names N. delognei and N.

pseudocomoides are proposed as replacements for N. greuillii and N. comoides respectively and types are cited.

KEY WORDS: - diatom taxonomy - Navicula - N. grevillii - N. comoides - N. delognei - N. pseudocomoides - electron microscopy - Schizonema.

CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . 128 Materials and methods . . . . . . . . . . . . . . . . . . . 129 Structural studies . . . . . . . . . . . . . . . . . . . . 129

Observations - light microscopy . . . . . . . . . . . . . . 129 Observations - electron microscopy . . . . . . . . . . . . . 131 Discussion of structure . . . . . . . . . . . . . . . . . 135

Nomenclatural problems . . . . . . . . . . . . . . . . . . 135

Possible alternative names . . . . . . . . . . . . . . . . . . 138 Conclusions . . . . . . . . . . . . . . . . . . . . . . 140 Acknowledgements . . . . . . . . . . . . . . . . . . . . 142 References 142

Derivation of the specific epithetsgreuillii and comoides . . . . . . . 135

. . . . . . . . . . . . . . . . . . . . . .

* Present address: Botany School, South Parks Road, Oxford OX1 3RA. 0024-4074/78/0076-0127/$02.00l0 0 1978 The Linnean Society of London

127

128 E. J . COX

INTRODUCTION

Navicula grevillii (C.A.Ag.) Heiberg and N. comoides (Dillwyn) H. & M. Peragallo are common marine littoral diatoms which occur both in mucilage tubes and as free individuals. When growing in tubes the cells form large colonies, which are easily visible with the naked eye and bear a superficial resemblance to some filamentous brown algae, such as Ectocarpus. As a result many colonies were collected and described by phycologists at the start of the nineteenth century (e.g. Agardh, 1817, 1824, 1830; Dillwyn, 1802-1809, and Greville, 1823-1828). A plethora of names accumulated because species were described on the basis of the morphology of the colonies, characteristics which can vary with the habitat.

Although the shape and structure of the enclosed cells, or their arrangement within the tube was sometimes described, the reliance on gross features resulted in the combination of species under a single name or the allocation of a single species to two or more Schizonema species. Several genera were described for the different colony forms, but with improvements in microscopy, detailed examination of the enclosed cells became possible and revealed anomalies in the earlier classifications. In addition, the discovery that free-living and tubedwelling individuals could have the same frustule structure caused genera based on the tube-habit to be abandoned (Heiberg, 1863; Cleve, 1894).

The taxonomic treatment of N. grevillii and N. comoides has not been consistent. Many authors have treated N. comoides simply as a variety of N , grevillii (e.g. Cleve, 1894; H. & M. Peragallo, 1897; Aleem, 1949), but others have considered that it warranted specific status (Smith, 1856; Hustedt, 1962; Hendey, 1964). The results of light and electron microscopical studies by the author support the separation of the two species while differences in tube form and habitat preference are cited as additional specific attributes (Structural studies).

Hustedt (1962) and Hendey (1964) both refer to Aleem’s work (1949) which includes a description of Agardh’s type material for Schizonema grevillii and S. comoides (Agardh, 1830). Each comments on the identity of these specimens, but while Hustedt retains the specific epithets grevillei and comoides, Hendey argues that, because the Agardh material contains neither species, new names are required for both. He renames them N. grevilleana and N. pseudocomoides, referring to Smith (1856) for illustrations and material but without citing lectotypes for either. Reexamination of the Agardh material bears out Hendey’s conclusion that different names are required. Van Landingham (1975) includes N. grevillei, N. comoides, N. grevilleana and N. pseudocomoides in his catalogue and indicates all as correct. Whilst all the names are effectively published they refer to only two species, therefore only one pair of names can possibly be correct, assuming that the conditions for valid publication are fulfilled in each case.

From illustrations in Smith & Sowerby (1790-1814), Lyngbye (1819), Greville (1823-1828) and Kutzing (1844) it seemed likely that other Schizonema species were synonymous with N. grevillii and N. comoides and therefore could offer alternative epithets to replace grevillii and comoides. These species have been examined from herbarium material, their identity established and their suitability as solutions to the nomenclatural problem

TAXONOMIC STUDIES O N NAVZCULA 129

considered. Such species were not mentioned by Hendey (1964) and he has since stated (personal communication) that he did not follow up the possible synonyms.

MATERIALS AND METHODS

I collected colonies of N. grevillii and N. comoides from a number of sites in southern England. Specimens were examined using light and electron micro- scopy (Cox, 1975) and carbon replicas were prepared using a technique modified from Drum (19671, shadowing with gold/palladium. When herbarium material was used, because of the small quantities available, these were cleaned overnight in 50% nitric acid in centrifuge tubes, washed in distilled water and centrifuged down between each washing.

Herbarium material from the Agardh Collection at Lund, Sweden, the Lyngbye Collection at Copenhagen, Denmark and from various collections in the British Museum (Natural History) were also examined. These were: Van Heurck Types du Synopsis No. 152 (Wynne Baxter collection 6152)-N. delognei; BM 18991-Schizonema quadripunctatum C.A.Ag.; BM 19049- Schizonema araneosum Kutz.; BM 24400 & 24402-Schizonema grevillii from the Smith collection; BM 24390 & 24391-Schizonema comoides from the Smith collection.

Drawings of cleaned frustules were made using a camera lucida attachment on a Leitz Laborlux microscope.

STRUCTURAL STUDIES

Observations-light microscopy

In the light microscope, cells of N. grevillii and N. comoides are easily recognised by their wide girdle regions and lobed chloroplasts, which Hendey (1964) has referred to as “butterfly” chloroplasts. When seen in girdle view the chloroplasts are indented in four places resembling the wings of a butterfly (Fig. lC, D). Hendey ( 1 9 5 1 ) has a number of figures showing these well. In valve view the chloroplasts are seen as two or four bands along the edges of the valve (Fig. l B , D). The cells are typically lanceolate or rhomboidal, although small cells of N. comoides may be almost eliptical. N. grevillii is the larger species, 30-80 pm x 13-18 pm, while N. comoides is smaller, 15-35 pm x 4.5-9 pm. In girdle view the cells may be almost as wide as they are long (Fig. 1 B, D). Hendey (personal communication) reported the occurrence on one occasion of a ‘giant’ strain of N. grevillii, 95-1 3 5 pm x 25-28 pm.

N. grevillii produces mucilage tubes which are generally wider than the enclosed cells, while the tubes of N. comoides are about as wide as the cells. The disposition of the cells within the tubes varies accordingly: N. grevillii cells are haphazardly arranged, while N. comoides cells are arranged in uniseriate rows (Fig. lA, D, E). The narrow tubes produced by N. comoides may be contiguous forming a compound tube. Additional sub-tubes are produced by dichotomies of the existing tubes following cell division, and may diverge to give a branched colony. N. grevillii can also form branched colonies. N. comoides colonies can often be recognized without recourse to microscopy

1 3 0 E. J . COX

because their filaments are coarser and more fibrillar than those of other tube-dwelling species.

Examination of cleaned material of both species, as described by Hustedt (1962) and Hendey (1964), reveals that the striae in N. grevillii are evenly

\

Figure 1. Camera lucida drawings: A-E, to show the arrangements of cells in their tubes, chloroplast structure and arrangement. A-C. N. grevillii. D, E. N . comoides, with an endotubular Nitzschia species also present. F-J. Drawings of cleaned valves. F, G . N. grevillii (van Heurck Type No. 152). €3. Girdle view of N. comoides. I , J. N. comoides valves. Scale lines represent 10 pm except in A where the scale line represents 100 pm.

TAXONOMIC STUDIES ON NAVICULA 131

Figures 2 to 4. 2, 3 . Light micrographs of cleaned valves of N. grevillii (BM slide 24402). 2 x3100, 3 x4600. 4. Light micrograph of cleaned valves of N. comoides (BM slide 19049 Type slide of Sch. avaneosum Kutz. x2100.

spaced while in N. comoides they are more widely spaced opposite the central area (Figs l F , G, I , J , 2, 3 and 4). In the latter the striae are clearly porate (Figs 1J and 4) while those of N. grevillii are very finely porate (Figs l G , 2 and 3). The numbers of striae in 10 pm are 16-20 in fi. grevillii and 16-18 in N. comoides. Both species have straight raphes which terminate before the valve apex, proportionally further from the apices in N. comoides than in N. grevillii (Fig. l F , G , I , J) . The apical raphe endings curve to one side (Fig. l F , G). InN. grevillii the central area of the valve is smaller than in N. comoides, but it is often more highly refractive, containing 1-3 pores (Fig. l F , G) which are absent from N. comoides valves (Fig. 11, J). Both have numerous girdle bands per valve and the raised central and polar raphe endings are often visible in girdle view (Fig. 1H).

0 bserva tions-electron microscopy

Although it provides little additional information on valve structure, transmission electron microscopy does elucidate pore sub-structure. The pores are circular or oval, occluded by a perforate pore plate (Figs 5 to 7), like those in Berkeleya spp. (Cox, 1975). In N. grevillii the sub-pores are approximately 6 nm in diameter and very regularly distributed in a hexagonal arrangement (Fig. 5 ) . In N. comoides the hexagonal pattern is less obvious because of the closer arrangement of the subpores (Fig. 6), which are themselves larger than those of N. grevillii (approximately 10 nm diameter). Rows of similar pores are present in each girdle band (Fig. 7). Carbon replicas of the internal central raphe endings of N. grevillii show the presence of elongated raised areas terminating the slits (Fig. 8). At higher magnifications the raised areas are found to contain a row of fine pores (Figs 9 and 10).

With scanning electron microscopy it is possible to see the apical curvature of the raphe with ease (Figs 11 and 12), and that the outer surface of the valve

9

132 E. J. COX

Figures 5 to 10. 5 t o 7. Transmission electron micrographs showing pore structure of N. grevillii ~ 9 0 , 0 0 0 (5), N. comoides ~44,000 (6), N. grevillii girdle band pores ~73,000 (7). 8 t o 10. Carbon replicas of the central internal raphe endings of N. grevillii. 8, ~25 ,000 . 9, 10, Details of 8. ~40,000.

is slightly depressed at the central raphe endings (Figs 11, 13 and 16). Scanning electron microscopy aIso confirms the presence of pores in the central nodule of N. grevillii (Figs 16, 20 and 22) and their absence from that of N. comoides (Figs 11 and 13).

Internally the raphe slit lies in a slightly thickened region. The thickening decreases near the central nodule, while at the poles the raphe slit terminates in

Figures 11 to 17. 11. SEM external view of N. comoides valve x2700. 12. SEM external polar raphe ending of N grevilfii ~10 ,200 . 13. SEM external central raphe endings of N. comoides ~13 ,800 . 14. SEM internal central raphe endings of N. comoides ~15,500. 15. SEM internal polar raphe ending of N. grevillii showing the helictoglossa x9900. 16. SEM external central raphe endings of N. grevilli showing pores in the central area. A girdle band series is also visible x5600. 17. SEM internal view of N. grevillii showing the raphe system and the elongated structures terminating the central raphe endings x2900.

TAXONOMIC STUDIES ON NA VICULA 1 3 3

134 E. J . COX

Figures 18 to 23. SEMs of N . guevillii. 18. External central raphe endings x8800. 9 . Internal central raphe endings x9400. 20. External central raphe endings X8600. 21. Internal central raphe endings x9100. 22. External central raphe endings ~ 5 5 0 0 . 23. Internal surface of girdle bands with pore plates still present x9200.

a helictoglossa, although this is only slightly raised (Figs 15 and 17). (For this structure in N. comoides see Cox, 1977c.) The central raphe endings of N. grevillii terminate internally in elongate raised structures (Figs 17, 19 and 21) which appear with scanning electron microscopy to contain a fine slit (Fig. 21). These structures are absent from N. comoides (Fig. 14). The lack of pore openings on the internal surface of the central nodule, combined with the correlation between this type of internal raphe ending and the external pores in

TAXONOMIC STUDIES ON NAVICULA 135

the central nodule, suggests that, together, these constitute a hitherto undescribed structure.

In some scanning electron micrographs the pore plates are visible. The pore plates are over the inner pore opening and are convex, the highest part being about level with the inner valve surface (Fig. 23). It is also possible to see and count the girdle bands associated with each valve (Figs 12, 16 and 23); there are usually six per valve.

Discussion o f structure

While N. grevillii and N. comoides have many features in common they are sufficiently distinct to warrant separation at the specific level. The most obvious difference, although not necessarily the most important, is that of size. This is correlated with varying valvar detail, different types of tube con- struction and with habitat preferences.

Hustedt (1962) and Hendey (1964) both consider that the wider-spaced striae at the centre of the valve of N. comoides and the more clearly porate nature of its striae enable this species to be distinguished easily from N . grevillii. Hendey (1964) cites the more slender outline of N. comoides and the position of the polar nodules as additional distinguishing characteristics. The presence of pores in the central nodule of N. grevillii recorded above is yet another structural feature which supports the separation into two species.

The observation of Aleem (1949) that the species have different habitat preferences is supported by Hendey (1964), while I have found that N. comoides occurs consistently lower in the littoral than N. grevillii, and does not extend as far upstream in estuarine situations as N. grevillii (Cox, 1977a, b). The difference in tube construction is another piece of evidence which supports the recognition of N. grevillii and N. comoides as discrete species.

NOMENCLATURAL PROBLEMS

Derivation of the specific epithets grevillii and comoides

N. grevillii (C.A.Ag.) Heiberg: The earliest specimen to bear the specific epithet grevillii is a species of Schizonema described by Agardh (1830) from material sent by Greville. The entry in Agardh’s Conspectus: 19 reads:

“Sch. Grevillii, filis capillaribus irregulariter ramosis, ramis erectis, cymbellis spar sis. Conf. comoides Engl. Bot. t. 1700 sec Grev. Monema comoides Grev. t. 368. Specimina misit Greville. Hanc speciem Grevillianam non esse Confervam Comoidem Dillwynii ex specimine a Borrero miso, ei ab ips0 Dillwynio dato, didici.”

In the Agardh herbarium there are two specimens, numbers 3758 and 3759, under the specific name Sch. grevillii Ag. These are both labelled Monema comoides Grev. with the location “Devonia” given. The specimens are alike but number 3759 has been designated the lectotype of Sch. grevillii C.A.Ag.

136 E. J. COX

The reference to Greville should read t. 358, there is no t. 368 in the Scottish Cryptogamic Flora. Greville’s description of Monema comoides is based on material collected at Sidmouth. Such a specimen was found in the British Museum (Natural History) labelled in Greville’s hand with the location Sidmouth, 1828, and this is an isotype of Sch. grevillii C.A.Ag.

Both the lectotype of Sch. grevillii C.A.Ag. in Agardh’s herbarium and the isolectotype in the British Museum (Natural History) labelled Monema comoides by Greville (BM Herbaxium and slide BM 78016) have been examined and found to contain cells of N. rarnosissima (C.A.Ag.) Cleve.

Conferva comoides from English Botany t. 1700 (Smith & Sowerby, 1790-1814) is given as a synonym of Sch. grevillii by Agardh (1830), presumably because Greville (1828) refers to it. However, the illustration in English Botany is of material collected by Borrer at Yarmouth in 1806, and there is a herbarium specimen in the British Museum (Natural History) of this gathering labelled “C. comoides Dillwyn 1803 t. 27”. Part of it was also sent by Borrer to Agardh, who noted that it differed from the Greville material. This gathering as represented both in the British Museum (Natural History) and Agardh’s herbarium is Berkeleya rutiluns (Trentepohl) Grun.

Heiberg (1863) transferred Sch. gvevillii t o Navicula Bory. He referred t o Sch. grevillii Ag. in Smith’s Synopsis (1856) P1. LVIII, fig. 354 (sic) but believed that Schizonema should be dropped as a generic name because the occurrence of cells in tubes is not a constant feature of any of the species included. The illustrations in Smith (1856) show both frustule structure and tube form, and his specimen is clearly representative of N. grevillii as understood by diatomists since. Examination of Smith’s slides (BM 24400 & 24402) bears this out.

N. comoides (Dillwyn) H. & M. Peragallo: Hustedt (1962) gives the authorities for N comoides as (Ag.?) Peragallo yet the Agardh references which follow do not include any to the name comoides although the reference to Dillwyn (1803) does. As it was Dillwyn who described Confervu comoides as a new species, the authorities should be as above. Agardh (1830) refers to Dillwyn (1802-1809, 1803) in his description of Sch. comoides and also in his descriptions of Scytonema comoides (Agardh, 1817, 1824) yet does not give Scytonema comoides as a synonym of Sch. comoides. The descriptions in the different Agardh works, with his synonymies are as follows:

Agardh 1817-Scytonema “1. comoides, caespite lax0 subferrugineo, filis flexuosis aureo fuscis, ramis solitariis remotiusculis adscendentibus. Con,fervu comoides Dillw. t. 27. Conferva radicuns Dillw. p. 57 t . C? Ad Ranen Norvegiae.”

Agardh 1824-“Scytonema conzoides, caespite lax0 subferrugineo, filis flexu- osis aureo-fuscis, ramis solitariis remotiusculis adscendentibus.

Conferva comoides Dillw. t. 27-E.B. t. 1700. non Gaill. Scytonemu comoides Ag.-Lyngb. Conferva araneosum Mohr sec Lyngb. In mari Septentrionali & Anglico.”

TAXONOMIC STUDIES ON NAVZCULA 137

Agardh 1830-“Sch. comoides filis setaceis, ramis simpliciusculis elongatis. Conferva comoides Dillw. t . 27. Bangia Gangilii Bonnem. msct. Ad rupes & Algas prope Swansea Angliae. Specimin authenticum a Dillwynio datum misit Borrer, quod cum specimine nomine Bangiae Gangilii a Bonnemaisonio dato apprime convenit.”

The inclusion of Conferva araneosum Mohr as a synonym of Scyt. comoides Ag. in Agardh (1824) follows its inclusion by Lyngbye (1819). Lyngbye gives the following as synonyms of Scyt. comoides Ag.: “Conferva comoides Dillw. (Dillwyn, 1803 t. 27 and Weber & Mohr Grossbritanniens Conferven), Conferva araneosa Mohr (Schrader, 1806) and Conferva rufa Roth (1806)”. However, in each case the earliest reference to comoides is Dillwyn (1802-1809, 1803) whose entry reads:

‘‘Conferva comoides Dillw. t. 27 June 1 1803. On several of the marine algae and rocks in the sea at Swansea.” One

specimen for t. 27 in Fascicle I11 of British Confervae is labelled “Swansea, April 1803” in Dillwyn’s handwriting and has therefore been designated the lectotype of Conferva comoides Dillwyn. When I examined this material, it was found to contain cells of Berkeleya rutilans (Trent.) Grun. Dillwyn’s illustration shows a tube with the enclosed cells in an arrangement typical of B. rutilans.

The Agardh herbarium contains two specimens under the name Sch. comoides; No. 3654-Sch. comoides Ag., Bangia Gangilion Bm in Armorica and No. 3655-Conferva comoides Dillw. misit Borrer. Both specimens are of B. rutilans and the latter is from the gathering of which English Botany t. 1700 (Smith & Sowerby, 1790-1814) was based. The entry in English Botany is as follows:

“C. comoides Dillwyn. Wm. Borrer jun. Esq., Yarmouth, Oct. 1806.”

(There is also a reference to Dillwyn’s original description, t. 27-marine on rocks at Swansea.)

Agardh does not seem t o have had a specimen sent by Dillwyn from Swansea. As mentioned under N. grevillii, the specimen of C. comoides (E.B.) was identified as B. rutilans and had been given as a synonym of Sch. grevillii by Agardh (1830). Therefore Agardh’s concept of Conferva comoides Dillw., on which he based the names Scytonema comoides and Schizonema comoides is based on a specimen which he also included in the synonymy of his Schizonema grevillii. However neither Agardh’s nor Dillwyn’s specimens with the specific epithet comoides would now be recognized as N. comoides.

Smith (1856) includes a description of Sch. comoides Ag. and as with his treatment of Sch. grevillii Ag., the illustrations enable this to be recognized. I t is N. comoides sensu Hustedt (1962). H. & M. Peragallo (1897) placed this species in Navicula but treated it as a variety, comoides, of N. grevillei in their text but as an independent species in the legend to their illustration. Aleem (1949) similarly regarded this as only a variety of N. grevillei although he left both under the generic name Schizonema.

138 E. J. COX

Under the International Code for Botanical Nomenclature (Stafleu et al., 1972), in order to be legitimate a name must be “effectively published in a form which complies with the provisions of Articles 16-17, be accompanied by a description and comply with Articles 33-45”. The names grevillii and cornoides were both validly published but because the type specimens are not in agreement with our present understanding of these species the names must either be used for the specimens in agreement with the types, or they must be abandoned.

Schizonema grevillii was published later than Schizonema ramosissimum C.A.Ag. (1824) and hence can be treated as a synonym of Navicula ramosissima (C.A.Ag.) Cleve. On the other hand Conferva comoides Dillw. antedates Conferva rzttilans Trentepohl in Roth (1797-1806, 1806: 179), but as Dillwyn’s name and the combinations based on it have been widely and persistently used for a taxon not including its type, this name is to be rejected under Art. 69 of the International Code of Botanical Nomenclature and placed on the list of nomina rejicienda provided for in the version of this Article adopted at the Leningrad Congress in 1975.

POSSIBLE ALTERNATIVE NAMES

Since neither grevillii nor comoides can be used as specific epithets for the species under consideration, alternative names must be found. Hendey (1964) proposed the names grevilleana and pseudocomoides, based on Smith material; however these can only be adopted in the absence of an earlier applicable synonym of Sch. grevillii and Sch. comoides sensu W. Smith. Earlier validly published names take priority over later ones (Stafleu et al., 1972). Therefore the early synonyms of Sch. grevillii and Sch. comoides were traced.

Van Landingham (1975) gives the following specific epithets as synonymous with grevillei: apiculatum, quadripunctata and delognei; and with comoides: apiculata, intricata, fastigatum and araneosum, To these may be added gangilion, radicans and rufa from the synonymies of Agardh (1830, 1817) and Lyngbye (1819) respectively. The epithet foetida used by Dillwyn (1802-1809, 1809) for a tubedwelling species, with extant material in the British Museum (Natural History) was also considered.

The following epithets had to be rejected because they are in current use for species of Navicula: apiculata, quadripuncata and intricata. Fastigatum was rejected because examination of a specimen of Micromegu fastigatum Kutz. showed that this contained cells of Navicula ramosissima. Bangia gangilion was a manuscript name only and never validly published. The remaining epithets will be discussed individually.

delognei: Van Heurck (1880-1885) figured (pl. XI, fig. 13; 1880) a diatom as Navicula delognei Van Heurck, of which he subsequently said, in the text under Schizonema grevillei (p. 110; 1885), “Des recherches post6rieures A la publication de L’Atlas nous ont demontrt que le Nav. Delognei (pl. XI, fig. 1 3 ) doit @tre considirk comme une forme du S. Grevillei”. The specimen of Schizonema grevillei distributed by Van Heurck as Types du Synopsis No. 152 shows that his concept of the species agreed with that of Smith (1856), and his

TAXONOMIC STUDIES ON NAVZCULA 139

figure of Navicula delognei is consistent with this. The name can therefore be taken to apply t o that species, for which it is correct.

araneosum: The specific epithet araneosum can be traced back to Mohr (1806) and Weber & Mohr (1803-1810) through the synonymies of Kutzing (1844), Agardh (1824) and Lyngbye (1819). The name Conferva araneosa is mentioned as a synonym of Conferva cornoides by Weber & Mohr and it occurs in a list of species collected from Schleswig-Holstein by Mohr, but no specific description is given and it was therefore not validly published. The use of the name Schizonema araneosurn by Kutzing (1844) accompanied by a description constitutes the first valid publication of this epithet. Unfortunately Kutzing cites Conferva comoides Dillw. and Schizonema comoides Ag. as synonyms in addition to Confervu araneosa Mohr, and hence this name is superfluous and illegitimate (Art. 63). Kutzing gives two figures for the species, one of which (t. 24 fig. 11) corresponds with N. comoides sensu Hustedt (1962) although the other (t. 25 fig. IX) is more like N. ramosissima. In the herbarium of the British Museum (Natural History) there is a specimen labelled by Kutzing “Cont araneosa Mohr, Con,f comoides Dillw. Mertens”. As Mohr (1806) gives the authority for his nomen nudum Conferva aruneosa as Mert. et Mohr, this presumably corresponds to their concept of the species. Kutzing’s number on this packet is 512 and the packet is also labelled by him “Tab. 24, fig. 11”. The specimens on the microscope slide prepared from this packet are Navicula comoides sensu Hustedt.

foetida: Dillwyn’s use of foetida as a specific epithet occurs in British Confervae t . 104 (1809). He describes a species from “Rocks near low water mark, under Mumbles light-house, Glamorgan”. The relevant specimen was found, signed by Dillwyn and labelled “C. foetida, Mumbles”. On examination this was found t o contain N. comoides cells. However Dillwyn did not regard this as a new species but as Ulva foetida, Vaucher (1803) in part on the basis that both had the same smell. Vaucher’s specimen was from freshwater while Dillwyn (1 809) had emphasized that his species occurred near low water mark. N. foetida is therefore an unacceptable epithet for a marine species, based on Dillwyn material, since the name originally referred t o a freshwater species and on grounds of habitat the two must be considered distinct.

C. foetidu has been included in the table of synonymy as, for completeness, have the various collections of Sch. quadripunctatum. Those Schizonema species which are actually N. ramosissirna (except grevillii and comoides) have not been included since it is hoped to deal with these in more detail later.

radicans: The epithet radicans was first used by Dillwyn (1809) with the accompanying description:

“C. filis ramosis hic illic radicantibus, strictis, rigidiusculis, fusco olivaceis; ramis simplicibus, sparsis, erectis, obtusis, basi a attenuatis; articulis diametro sub-dimido brevioribus. TC.” The illustration shows a filamentous alga, very unlike a tubedwelling diatom. Harvey (1841) gives “Conf. radicans Dillw.” as a synonym of Sphacelaria radicans (Dillw.) Ag. De Toni (1889-1907) similarly gives radicans as an epithet of Sphacelaria (Phaeophyceae), synonymous with C. olivacea Dillw. which is also illustrated in English Botany (Smith & Sowerby,

140 E. J . COX

1790-1814) t . 2138. The original plates for the latter were located but it was discovered that the original material for these had been removed and no other could be found.

On the basis of the illustrations and the synonymy it is unlikely that this name ever referred to a tubedwelling diatom and it should therefore be rejected as a name for the latter.

rufa: Roth (1806) used the name Corzferva rufa for a marine alga collected in 1802 and stated that it resembled C. comoides Dillw. but was distinct. Dillwyn (1802-1809, 1809) considered it probable that C. rufa was a synonym of C. comoides. If we accept this identification, N. rufa would not apply to N. comoides as described above (structural studies). The name is not found elsewhere and in the absence of Roth material it cannot be applied to any species.

grevilleana and pseudocomoides: Hendey (1964) substituted these epithets for Schizonema grevillii sensu W. Smith and Schizonema comoides sensu W. Smith. Navicula grevilleana Hendey is not validly published since there is no latin description nor any designation of type, nor is it a name published as substitute for a previously published name applying to the same taxon; Hendey quotes only misapplications as synonyms. However, he cites Schizonema grevillei var. comoides Aleem as a synonym of his N. pseudocomoides. Aleem (1949), when publishing his name, indicated that it was based on Schizonema comoides sensu W. Smith and not on Conferva comoides Dillw. It is therefore t o be regarded as the name of a new variety, and, at the date of its publication, its English description was sufficient to give it valid publication. Navicula pseudocomoides Hendey is thus a validly published name and the correct one for Schizonema comoides sensu W. Smith. W. Smith's slide from the coast of Sussex (BM 24390) seems an appropriate lectotype and is here designated as such.

CONCLUSIONS

As explained by Hendey (1964) the names N. grevillii and N. comoides cannot be used for the species described above. N. delognei Van Heurck (Van Heurck Types du Synopsis No. 152) should be adopted to replace N. grevillii while N. pseudocomoides Hendey (BM 24390) should replace N. comoides.

Navicula delognei H. Van Heurck, Synopsis des Diatombes de Bblgique. P1. XI, fig. 1 3 (1880): 110 (1885).

Schizonema grevillii sensu W. Smith, Synopsis of British Diatomaceae: 77 (1 85 6). Navicula grevillei sensu Hustedt, Die Kieselalgen, in Rabenhorst 's Krypto- gamen Flora, Band VII, Teil3, Lieferung 2: 302 (1962). Navicula grevilleana Hendey, A n introductory account of the smaller algae of British Coastal Waters. Part V. Bacillariophyceae (Diatoms): 191 (1964).

ICONES. Van Heurck, P1. XI, Fig. 1 3 (1880); Smith, P1. LVIII, Fig. 364 (1856); Hustedt, Fig. 1422 (1962); Hendey, P1. XXX, Fig. 1 (1964).

TAXONOMIC STUDIES ON NAVZCULA 141

Table 1. Table of synonymy

Specific name Published Original collection Location of material Correct identification

Conferva comoides

Conferva comoides

Con ferva ru f a

Dillwyn 1803 t. 27 E.B. 1700 1806

Roth 1806 p. 280

Dillwyn-marine o n rocks at Swansea Borrer, Yarmouth 1806

Roth-island of Fehmarn, Baltic Sea

Conferva foetida

Conferva foetida

Conferva radicans

Bangia quadripunctatum

Schizon ema

Monema quadripunctatum quadripunctatum

Monema comoides

Sc hiz on ema grevillii

Schizonema comoides

Schizonemu comoides (Bangia gungilion)

Schizonema araneosum

Schizonema comoides

Schizonema grevillii

Navicula delognei

Dillwyn 1809 t. 104 E.B. 2101

Dillwyn 1809 p. 57, tC

Lyngbye 1819 t. 26 Agardh 1830

Greville 1828 t. 286

t. 358

Agardh 1830 p. 19

Agardh 1830 p. 19 (Bonnem. )

p. 10

Greville 1828

Kiitzing 1844 p. 113, t . 24 Fig. I 1 Smith 1856 f358

Smith 1856 f364 Van Heurck 1880

Dillwyn, Mumbles

Hooker-Cley, April 1808

-

Hofmansgave, Denmark 1816

-

Appin, Scotland

Sidmouth 1828

G reville

Borrer

Bonnemaison, Brittany

Mertens, Schleswig-Holstein

Smith, Sussex, 1854

Smith, Pevensey

Van Heurck

BM-Dillwyn fascicle 111

BM Herbarium (Type)

not found

BM Herbarium BM slide 78015 BM Herbarium

lost

Copenhagen Lyngbye Collection BM slide 18991

BM Herbarium BM slide 78016

Lund Agardh Herbarium 3758, 3759

Lund Agardh Herbarium 3655 Lund Agardh Herbarium 3654

BM slide 19049

BM slides 24390 (type) 24391

BM slides 24400. 24402

Van Heurck SBD 152 BM Wynne Baxter collection 6152

Berkeleya rutilans (Trent) Grun. B. rutilans

Cannot be identified but presumed B. rutilans

N. pseudocomoides Hendey B. rutilans

presumed Sphacelaria sp.

N. delognei Van Heurck B. rutilans

N. delognei Van Heurck

N. ramosissima (Ag.) Cleve

N. ramosissima

B. rutilans

B. rutilans

N . pseudocomoides

N. pseudocomoides

N. delogn ei

N. delognei

TYPUS. Van Heurck, Types du Synopsis No. 152. LOCUS. England. HOSPIS. Marine, littoral, on rocks or other algae often in mucilage tubes.

Navicula pseudocomoides Hendey, An introductory account of the smaller Algae of British Coastal Waters. Part V. Bacillariophyceae (Diatoms): 192 (1964).

Schizonema comoides sensu W. Smith, Synopsis of British Diatomaceae: 75 (1856). Navicula grevillei var. comoides Aleem, Botaniska Notiser, 102: 427 (1949). Navicula comoides sensu Hustedt, Die Kiesselalgen, in Rabenhorst 's Krypto- gamen Flora, Band VII, Teil 3, Lieferung 2: 304 (1962).

142 E. J . COX

ICONES. Hendey, P1. XXX, Fig. 2 (1964); Smith, P1. LVII, Fig. 358 (1856); Hustedt, Fig. 1423 (1962).

TYPUS. BM slide 23490. LOCUS. Sussex. HOSPIS. Marine, lower littoral, on rocks or other algae, often in mucilage

tubes.

Table 1 shows the publication of the various names mentioned in this paper, the original collector, present location of extant material and the correct identification of the specimens.

ACKNOWLEDGEMENTS

I should like to thank especially Mr R. Ross, for his interest in this work and for his expert advice on the application of the International Code of Botanical Nomenclature and Mr N. I. Hendey for his suggestions. Dr 0. Almborn and Mr J. B. Hansen very kindly made available material from the Agardh Herbarium, Lund, and the Lyngbye collection, Copenhagen, respectively, while Miss P. A. Sims gave invaluable assistance with the British Museum (Natural History) collections.

REFERENCES

AGARDH, C. A., 1817. Synopsis Algarum Scandinaviae. Lundae. AGARDH, C. A., 1824. Systema Algarum. Adumbravit C-A- Agardh. Literis Berlingianis. Lundae. AGARDH, C. A., 1830. Conspectus Criticus Diatomacearum. Lundae. ALEEM, A. A., 1949. Distribution and ecology of marine littoral diatoms. Botaniska Notiser, 102:

414-440. CLEVE, P. T. 1894. Synopsis of the naviculoid diatoms. Konglica Svenska Vetenskaps-Akademiens

Handlinger, 26: 1-194. COX, E. J. 1975. A reappraisal of the diatom genus Amphipleura Kutz. using light and electron

microscopy. British Phycological Journal, 10: 1-12. COX, E. J. , 1977a. The distribution of tube-dwelling diatom species in the Severn Estuary. Journal of the

marine biological Association of the United Kingdom, 57: 19-27. COX, E. J., 1977b. The tube-dwelling diatom flora a t two sites in the Severn Estuary. Botanica Marina,

COX, E. J., 1977c. Raphe structure in Naviculoid diatoms as revealed by the Scanning Electron Microscope. Proceedings of the Fourth Symposium on Recent and Fossil Marine Diatoms, Nova Hedwigia Beiheft, 54: 261-274.

20: 111-119.

DE TONI, G. B., 1889-1907. Sylloge Algarum omnium hucusque cognitorum, 5 vols. Pavia. DILLWYN, L. W., 1802-1809. British Confervae. London. DRUM, R. W., 1967. Carbon replicas of siliceous sponge spicules. Science, New York, 157: 581-582. GREVILLE, R. K., 1823-1828. Scottish Cryptogamic Flora, 6 vols. Edinburgh: Maclachlan & Stewart. HARVEY, W. H., 1841. A Manual of the British Algae. London: John van Voorst. HEIBERG, P. A. C., 1863. Conspectus critrcus Diatomacearum Danicarum. Copenhagen. HENDEY, N . I., 1951. Littoral diatoms of Chichester harbour with special reference to fouling. Journal

HENDEY, N. I., 1964. A n Introductory Account of the smaller Algae of British Coastal Waters. Part V.

HEURCK, H. VAN, 1880-1885. Synopsis des Diatomkes de BPlgique. Anvers: Ducaju e t Cie. HUSTEDT, F., 1962. Die Kieselalgen. In Rabenhorst’s Kryptogamen Flora, Band VII. Leipzig. KUTZING, F. T., 1844. Die Kieselschaligen Bacillarien oder Diatomeen. Nordhausen: Kohne. LYNGBYE, H. C., 1819. Tentamen Hydrophytologiae Danicae. Hafniae. MOHR, D. M. R., 1806. Schleswig-Holsteinische Algae aquaticae. Neues Journal fur die Botanik, 1 : 196. PERAGALLO, H. & PERAGALLO, M., 1897. Diatomkes marines de France et des districts maritimes

woisins. Grez-sur-Loing (S.-et-M.): M. J. Tempere. ROTH, A. G., 1797-1806. Catalecta Botanica. Lipsiae.

of the Royal Microscopical Society, 71: 1-86.

Bacillariophyceae (Diatoms). London: FIMSO.

TAXONOMIC STUDIES ON NAVICULA 143

SMITH, J . E. & SOWERBY, J., 1790-1814. English Botany: or, Coloured Figures of British Plants, with their Essential Characters, Synonyms, and Places of Growth. London: J . Sowerby.

SMITH, W., 1856. Synopsis of British Diatomaceae, Vol. 11. London: Jan van Voorst. STAFLEU, F. A. etal., 1972. International Code ofBotanicalNomenclature (1972) as adopted by the XI

VAN LANDINGHAM, S. K., 1975. Catalogue of the Fossil and Recent Genera and Species of Diatoms

VAUCHER, J. P. E., 1803. Histoires des Conferves d’eau douce. Geneve: Chez J . J . Paschoud, Libraire. WEBER, F. & MOHR, D. M. H., 1803-1810. Grossbritanniens Conferven. Gottingen.

International Botanical Congress, Seattle, 1969. Oosthoek, Utrecht.

and their Synonyms. Part V. Navicula. Germany: J . Cramer.