. ; D o! tr m r=l D D m D THE RAY SOCIETY 7 INSTITUTED MDCCCXLIV. This volume is issued to the Subscribers to the RAY SOCIETY for the Year 1905. LONDON: MDCCCCV. A MONOGRAPH OP THE BRITISH DESMIDIACE^l BY W. WEST, F.L.S., Ex-president of the Yorkshire Naturalists' Union; Lecturer in Botany, Biology, and Bacteriology at the Technical College, Bradford ; AND G. S. WEST, M.A., F.L.S., A.R.C.S., Professor of Natural History at the Royal Agricultural College, Cirencester ; Formerly Scholar and Hutchinson Research Student of St. John's College, Cambridge VOLUME II LONDON PRINTED FOR THE RAY SOCIETY 1905 PRINTED BY ADLARD AND SON, LONDON AND DORKING. CONTENTS OF VOL. II. PAGE FAMILY DESMIDIACE.E. SUB-FAMILY II. PLACODERM^:. TRIBE 5. COSMARI.E (continued). GENUS 13. EUASTRUM . 1 14. MlCRASTERIAS . 76 15. COSMARIUM . 125 J ERRATUM. p. 7, line 4, for fig. 4 read fig. 6. LIST OF THE PLATES. PLATE XXXIII. Figs. 1-3. — Euastrum ventricosum (p. 4) ,, 4-8. — E. crassum (p. 5) PLATE XXXIY. Figs. 1-2. — Euastrum humerosum (p. 8) ,, 3-6. — E. pinnatum (p. 10) ,, 7-10. — E. obloncjum (p. 12) PLATE XXXY. Figs. 1-2. — Euastrum obloncjum (p. 12) „ 3-7.— E. Didelta (p. 15) ,, 8-10. — E. ampullae eum (p. 19) „ 11-12.— #. affine (p. 17) PLATE XXXYII — continued. Figs. PLATE XXXYI. 1-3. — Euastrum sinuosum (p. 20) 4. — 17. Jenneri (p. 22) 5-6. — 17. aboense (p. 23) 7-8. — E. inerme (p. 24) 9. — E. cuneatum (p. 25) 10-15.— E. ansatum (p. 27) 16-17.— E. obesum (p. 29) Figs. PLATE XXXYII. 1 . — Euastrum pinyue (p. 30) 2-5. — E. insigne (p. 31) 6. — E. intermedium (p. 33) 7. — E. Webbianum (p. 34) 8. — E. Sendtnerianum (P- 34) Figs. 9-10.- „ 11-13, „ 14-15, 16-19, -E. Turneri (p. 37) -E. rostratum (p. 35) -E. spinosum (p. 38) -E. bidentatum (p. 39) Figs. PLATE XXXYIII. 1-2. — Eua strum pidiun (p. 41) 3-4. — E. divaricatum (p. 42) 5-11.— E. dubium (p. 43) 12-13.— E. erosum (p. 45) 14-15. — E. pulcliellum (p. 46) 16-27.— #. elegans (p. 48) 28-36.— E. binale (p. 51) 37. — E. minutissim um (p. 57) PLATE XXXIX. Figs. 1-5. — Euastrum denticu- latum (p. 57) ,, 6-7. — E. incavatum (p. 58) „ 8-9. — E. montanum (p. 58) „ 10-16. — E. pectinatum (p. 60) ,, 17-18. — E. crassangulatum (p. 70) ,, 19. — E. gemmatum (p. 63) ,, 20. — E. occidentale (p. 67) PLATE XL. Figs. 1-7. — Euastrum verrucosum (p. 64) „ 8. — E. Cornubiense (p. 70) „ 9-10.— E. crassicolle (p. 71) ,, 11-14. — E. insidare (p. 68) „ 15-18. — E. crispulum (p. 72) „ 19-20 --E. svblobatum (p. 74) „ 21-22.— E. validum (p. 75) Vlll LIST OF THE PLATES. PLATE XLI. Figs. 1-6. — Micrasterias oscitans (p. 78) „ 7-13.— M. pinnatifida (p. 80) PLATE XLIL Figs. 1-9. — Micrasterias truncata (p. 81) „ 10-13.— M. crenata (p. 85) ,, 14. — M. Jenneri (p. 86) PLATE XLIII. Figs. 1-3. — Micrasterias Jenneri (p. 86) „ 4-11.— M. conferta (p. 88) PLATE XLIY. Figs. 1-7. — Micrasterias papilli- fera (p. 91) PLATE XLY. Figs. 1-4. — Micrasterias Murrayi (p. 93) „ 5-6. — M. truncata (p. 82) ,, 7. — Euastrum sublobatum (p. 73) PLATE XLYI. Figs. ' 1-4. — Micrasterias Sol (p. 95) „ 5-6. — M. apiculata (p. 97) PLATE XLYII. Figs. 1-7. — Micrasterias apiculata (p. 97) PLATE XLYIII. Figs. 1-6. — Micrasterias rotata (p. 102) PLATE XLIX. Figs. 1-7. — Micrasterias denticu- lata (p. 105) PLATE L. Figs. 1-7. — Micrasterias denticu- lata (p. 105) PLATE LI. Figs. 1. — Micrasterias cornuta (p. 124) ,, 2. — M. verrucosa (p. 109) ,, 3-6. — M. Tliomasiana (p. 110) „ 7. — M. TJwmasiana-den- ticulata (p. 112) PLATE LII. ; Figs. 1-9. — Micrasterias radiata (p. 113) Figs. 1-3.- 4-6.- PLATE LIII. -Micrasterias Crux- inelitensis (p. 116) -M.Americana (p. 117) PLATE LIV. Figs. 1-6. — Micrasterias Ameri- cana (p. 117) 7-8.— M. Maliabulesh- •warensis (p. 122) PLATE LV. Figs. 1-3. — Micrasterias MaJiabu- lesliwarensis (p. 122) „ 4. — Euastrum crassum (p. 8) PLATE LYI. Figs. 1-4. — Cosmarium obsoletum (p. 1 33) „ 5-7. — C. Smolandicum (p. 134) ,, 8-10. — C. taxiclwndriforme (p. 136) ,, 11-14. — C. circular e (p. 336) LIST OF THE PLATES. IX PLATE LVIL PLATE LXI — continued. Figs. 1-6. — Cosmarium Lundellii Figs. 36-37. — C. subcontractum (p. 138) ,, 7-9. — C. pacliydermum (p. 139) 10.— C. Balffii (p. 141) PLATE LYIII. Figs. 1-3. — Cosmarium Balfsii (p. 141) -C.perforatum (p. 143) ,, 6-7. — C. ocellatum (p. 144) ,, 8-12. — C. cyclicum (p. 145) PLATE LIX. Figs. 1-12. — Cosmarium undu- latum (p. 148) ,, 13-15. — C. subundulatum (p. 151) ,, 16-17. — C. -fontigenum (p. 147) „ 18-22.— CJCucumis (p. 152) PLATE LX. Figs. 1-4. — Cosmarium Subcu- cumis (p. 155) „ 5-10. — C. microspliindum (p. 156) ,, 11. — C. morsmn (p. 157) „ 12-17.— C. Pliaseolus (p. 158) „ 18-19.— C. tumidum (p. 160) ,, 20. — C. Trafalgaricwn (p. 161) ,, 21-23. — C. melanosporum (p. 162) „ 24-2 /. — C. aspliterosporum (p. 163) PLATE LXI. Figs. 1-2. — Cosmarium incon- spicuum (p. 164) ,, 3-11. — C. bioculatum (p. 165) „ 12-15.— C. tenue (p. 167) „ 16-20.— C. tinctum (p. 168) „ 21-22.— C. Havvm (p. 170) „ 23-35.— C.'contractum (p. 170) (p. 174) ,, 38. — C. subaversum (p. 174) PLATE LXII. Figs. 1. — Cosmarium tetra- cliondrum (p. 175) „ 2-10.— C. depressum (p. 176) ,, 11—13. — C. subquadrans (p. 178) ' ,, 14-16. — C. succisum (p. 179) „ 17-18 --C.retusiforme (p. 180) ,, 19. — C. sv.br etusi for me (p. 180) „ 20-25.— C. Hammeri (p. 181) ,, 26-27. — C. Nymannianum (p. 184) „ 28-30.— (7. trilolulatum (p. 185) PLATE LXIII. Figs. 1-10. — Cosmarium granatum (p. 186) „ 11-15. — C. Pokornyanum (p. 190) ,, 16-17. — C.pseudatlantlioideum (p. 191) ,, 18-23. — C. subtumidum (p. 192) „ 24-25.— C. galeritum (p. 194) ,, 26-30. — C. pseudonitidulum (p. 195) PLATE LXIY. Figs. 1-3. — Cosmarium nitidu- lum (p. 197) „ 4. — C. canaliculatum (p. 198) ,, 5-8. — C. pyramidatum (p. 199) ,, 9-13. — C. pseudopyramida- ttnn (p. 201) „ 14-16.— C. variolatum (p. 203) 17. — Euastrum pulcJiellum (p. 46) (x) ADDITIONAL BIBLIOGRAPHY. (SEE VOL. I, PP. xvii-xxxvi.) WEST & G. S. WEST, Freshw. Alg. Orkneys and Shetlands. — W. West and Gr. S. West, Freshwater Algre from the Orkneys and Shetlands. Trans. Botan. Soc. Edinburgh, XXIII, Oct. 1905. WEST & Gr. S. WEST, Further Contrib. Freshw. Plankton Scott. Lochs. — W. West and Gr. S. West, A Further Contribu- tion to the Freshwater Plankton of the Scottish Lochs. Trans. Roy. Soc. Edinburgh, XLI, 1905. BRITISH DESMIDIACE.E. Genus 13. EUASTRUM Ehrenb., 1832. Ehrenb. Entwick. Lebends. d. Infus. 1S32, p. 82 (in part). Ehrenb. Infus. 1838, p. 160. Ealfs in Ann. Mag. Xat. Hist. 1844, p. 187. Ealfs, Brit. Desin. 1848, p. 78. De Baiy, Conj. 1858, p. 50, 70-71. Arch, in Pritch. Infus. 1861, pp. 720, 728. Eabenh. Flor. Europ. Algar. Ill, 1868, p. 179. Wolle, Desm. U.S. 1884, p. 97. Cooke, Brit. Desin. 1886, p. 63. Hansg. Prodr. Algenfl. Bohm. 1888, p. 203. De Toni, Syll. Alg. 1889, p. 1065. G. S. West, Treatise Brit. Freshw. Alg. 1904, p. 164. Cells of variable size, longer than broad, compressed, deeply constricted in the middle, sinus generally linear (rarely open) ; semicells commonly truncate-pyramidate, apex with a median incision of variable depth, sometimes scarcely evident or absent, lateral mar sins entire, •/ o sinuate, or variously lobed, at or near the centre of the semicells v:ith one or more somewhat hemispherical pro- tuberances (or tumours) variously disposed; vertical view more or less elliptical, with one or more pro- tuberances on each side ; one chloroplast in each semi- cell, often irregularly lobed and ridded, with a sinsrle O »/ O o central pyrenoid in the small species, and a number of scattered ones in the large species. Zygospores globose, ellipsoid, or oblong-ellipsoid, ornamented with numerous conical papillae, or with simple (or furcate) spines. 1 2 BRITISH DESMIDIACEJ1. The genus Euastrum is separated from the preceding genera of the Cosmarieas by the relatively short, compressed cells. It resembles Tetmemorus in the presence of the apical notch, but differs in its short, compressed cells, with sinuate or lobed margins and central protuberances (or tumours) . Euastrum includes a great variety of species, some of which are transitional forms connecting it with other genera, such as Cosmarium and Micrasterias. E. verrucosum is the only British species connecting it with Micrasterias, but quite a number of British species connect the genus with Cosmarium ; such (for example) are, — E. occidentale, E. montanum, E. Cormibiense, and E. crispulum. Most of the species are lobed, some more than others, and there is always an odd number of lobes. The unpaired lobe at the apex of the semicell is always termed the polar lobe ; the others are known as lateral lobes. The name "Helierella }:' (Bory, ' Dictionnaire classique d'His- toire naturelle/ 1826, vol. viii, p. 98) which was revived by O. Kuntze (' Revis. gen. plant/ 1891, p. 897, etc.) is absolutely useless as a generic name. It is impossible to establish a genus on the remarks made by Bory, and Kuntze's genus Helierella includes two well-defined and well-known genera of Desmids. There are 40 British species, less than half of which can be considered as common. They can be conveniently arranged, with due consideration of their relationships, as follows : — SECTION A. Polar lobe with a distinct median notch, often deep and linear. a. Cells generally large (length 50 — 205/i), polar lobe short ; cell-wall usually punctate or scrobiculate ; external angles of polar lobe rounded. * Lateral margins lobed or sinuate. 1. E. ventricosum. 2. E. crassum. 3. E. humerosum. 4. E. pinnatum. 5. E. oblongum. 6. E. Didelta. 7. E. affine. 8. E. ampullaceum. 9. E. sinuosum. 10. E. Jenneri. 11. E. aboense. 12. E. inerme. ** Lateral margins entire. 13. E. cuneatum. 14 E. ansatum. 15. E. obesum. 16. E. pingue. EUASTRUM. 6 /3. Cells of medium size (length 26 — 135 /u), polar lobe distinctly elongate ; cell- wall smooth or scrobicu- late ; external angles of polar lobe rounded. 17. E, insigne. 18. E. intermedium. 19. E. Webbianum. y. Cells generally small (length 10 — 79^); cell-wall smooth, granulate, or spinous ; external angles of polar lobe usually furnished with a spine. * Lateral margins creuate, lobed, or sinuate. t Margins crenate. 20. E. Sendtnerianum. ft Margins lobed or sinuate. 21. E. rostratum. 22. E. Turnerii. 23. E. spinosum. 24. E. bidentatum. 25. E. pictum. 26. E. divaricatum. 27. E. dubium. 28. E. erosum. ** Lateral margins usually without lobes. 29. E. pulcliellmn. 30. E. elegans. 31. E. Unale. 32. E. denticulatum. 33. E. minutiasimum. 34. E. incavatum. 35. E. montanum. SECTION B. Polar lobe entire, generally somewhat retuse in the middle. a. Cells large, 48 — 114 /u in length. * Margin distinctly lobed. f Cell-wall smooth. 36. E. pectinaium. tt Cell- wall granulate. 37. E. gemmatum. 38. E. verrucosum. ** Margin not lobed ; cell- wall granulate. 39. E. occidental, p. Cells small, 17'5 — 48 ^ in length. * Seinicells distinctly three-lobed. 40. E. insulare. 41. E. crassangulatum . 42. E. Cornubiense. ** Seinicells not distinctly three-lobed. 43. E. crassicolle. 44. E. crispulum. 45. E. snblobatum. 46. E. validum. 4 BRITISH DESMIDIACE.E. 1. Euastrum ventricosum Lund. (PL XXXIII, figs. 1-3.) ? Euastrum crassum (Breb.) Kiitz. var. /3 Kalfs, Brit. Desm. 1843, t. 11, f. 3e,/. Euastrum ventricosum Lund. Desm. Suec. 1S71, p. 18, t. 2, f . 2 ; Wolle, Desm. U.S. 1884, p. 160 ; Cooke, Brit. Desm. 1886, p. 67, t, 33, f. 1 ; Wolle, Freshw. Alg. U.S. 1887, p. 38, t. 58, f. 1-3 ; De Toni, Syll. Alg. 1889, p. 1090; West, Alg. N. Wales, 1890, p. 287; Alg. W. Ireland, 1892, p. 137 ; Roy & Biss. Scott. Desm. 1893, p. 178 ; Nordst, Index Desm. 1896, p. 267 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alg. N. Ireland, 1902, p. 28. Helierella ventricosa Kuntze, Kevis. gen. plant. 1891, p. 899. Cells rather above the medium size, 1^ times longer than broad, deeply constricted, sinus narrowly linear ; semicells in front view somewhat semi-elliptical, strongly dilated at the base, unequally three-lobed, the inter- vening incisions narrow ; polar lobe smaller than lateral lobes, strongly convex, with a deep and narrow median incision, from vertical view oblong- elliptic with deeply emarginate poles ; lateral lobes bilobulate, with a broad median hollow, upper lobule obtuse and from the side view entire, lower lobule subtriangular with basal angles somewhat rounded; semicells with three tumours across the base and two across the middle. Side view of semi- cell somewhat pyramidate, with a protuberance on each side below the middle ; apex dilated, truncate, with rounded angles. Vertical view angular-elliptic, showing- five undulations on each side. Cell- wall punctate. Zygospore globose, furnished with large pointed teeth which are mostly curved (about twelve teeth visible around the margin). Length 80-136 ^ ; breadth 52-80 /x ; breadth of isthmus 18-28 /A; thickness 33-48 /i; cliam. zygosp., with teeth, about 110 p.. ENGLAND. — Near Bowness, Westmoreland (Bissetfy. Hawkshead, Lancashire ! Thursley Common, Surrey ! Near Bovey Tracey, Devon (Bennett). WALES. — Llyn Teyrn, Snowdon, bog above Capel Curio; Lakes, Carnarvonshire ! Dolg;elly, Merioneth ! o O */ • SCOTLAND. — Sutherland Inverness ! Aberdeen ! BUASTRUM. 0 Kincardine, Perth ! Argyll, Arran (Roy $* Bissett). Ross and Skye ! General and often abundant in the Outer Hebrides ! IRELAND. — Louo-h Macsrath and near Duno-loe, O O O Donegal ! Xear Foxford, Mayo ! Ballvnahinch, Kyle- II V I/ more, and Lakes near Recess, Gahvay ! Carrantuohill ' V and near Castletown, Kerry! Dublin and Wicklow (Archer). Geogr. Distribution. — Sweden. India (var.). United States. This characteristic species is somewhat rare in the British Islands. In some parts of the west of Ireland, Skye, and in the Outer Hebrides, it occurs in large quantity along with E. inerme (Halt's) Lund. It is considerably smaller than E. crassum, of different pro- portions, and differs considerably in its lateral lobes, the upper lobules of which are entire. "\Volle observed the zygo- spore from Florida, U.S.A. 2. Euastrum crassum (Breb.) Ktitz. (PL XXXIII, figs. 4-6.) Heterocarpella crassa Breb. in Cheval. microscop. et usage, Paris, 1839, p. 272 (name). Cosmarium crassum Breb. in Meuegh. Synops. Desm. 1840, p. 222. Euastrum Pelta Ralfs in Ann. Mag. Xat. Hist,, xiv, 1844, p. 190, t. 7, f. 1. Euastrum crassum (Breb) Ktitz. Phycol. germ. 1845, p. 135; Ealfs, Brit, Desm. 1848, p. 81, t. 11, f. 3 ; Arch, in Pritcli. Infus., 1861, p. 728 ; Eabenh. Flor. Europ. Algar. Ill, 1868, p. 181 ; Liind. Desm. Suec. 1871, p. 17, t. 1, f. 10 ; Kirchn. Alg. Schles. 1878, p. 157 ; Wolle, Desm. U.S., 1884, p. 97, t. 25, f. 1-3 ; Cooke, Brit. Desm. 1886, p. 65, t. 32, f. 1 ; Hansg. Prodr. Algenfl. Bohni. 1888, p. 205 ; De Toni, Syll. Alg. 1889, p. 1088; West, Alg. X. Wales 1890, p. 287, t. 6, f. 33; West, Alg. W. Ireland, 1892, p. 136 ; Roy & Biss. Scott. Desm. 1893, p. 176; West & Li. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Torks. 1900, p. 60 ; Alg. N. Ireland, 1902, p. 27. E. crassum var appendiculatum Breb. Liste Desm. 1856, p. 122. E. crassum b. majus Rabenh. Flor. Europ. Algar. Ill, 1868, p. 182. E. crasso-humerosum Benn. in Ann. Bot. iv, 1889, p. 171 ; in Journ. Eoy. Micr. Soc. 1890, p. 7, t, 1, f. 14 (figure bad ! ). Helierella crassa Kuntze, Eevis. gen. plant. 1891, p. 898. Euastrum magnificum Wolle var. crassoides Wolle, in Hastings' 'Desm. New Hampsh./ Amer. Month. Micr. Journ. 1892, p. 153, f. 1. (Vide West. & G. S. West in Journ. Bot. 1895, p. 67.) Cells large, almost twice as long as broad, elliptic- oblong, deeply constricted, sinus narrowly linear ; semicells in front view unequally three-lobed, inter- 6 BRITISH DESMIDIACE^l. veiling incisions narrow, closed or slightly open ; polar lobe smaller than the lateral lobes, convex and broadly cnneate, with a deep and narrow median incision, from vertical view oblong- elliptic with deeply emarginate poles ; lateral lobes very broad, sides broadly hollowed (sometimes with a rounded lateral projection), angles rounded ; semicells with three prominent protuber- ances across the base and two very slight tumours across the middle. Side view of semicell subpyrami- date, with subrectangular basal angles and a rounded- truncate apex, the upper lateral lobule emarginate and the lower one entire. Vertical view oblong-elliptic, with a slight protuberance at each pole and one in the centre of the convex sides. Cell-wall punctate, angles of lobes strongly thickened. Zygospore unknown. Length 163-205 /x; breadth 79-106 /x; breadth of isthmus 24-30 p, ; thickness 56-75 ^. ENGLAND. — Cumberland ! Westmoreland ! (Ralfs). W. and N. Yorks ! Lancashire ! Wilts ! Surrey ! Sussex ! (Rolfs). Kent ! (Ralfs). Hants ! (Rolfs). Devon! (Bennett). Cornwall. WALES. — General in Carnarvonshire (Glyder Fach at 2,200 ft.) ! Dolgelly, Merioneth ! SCOTLAND. — General! (Roy $ Bissett). IRELAND. — Donegal ! Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Down ! Geogr. Distribution. - France. Germany. Galicia in Austria. Italy. Norway. Sweden. Denmark. Finland. Poland. Faeroes. India. United States. E. craasum is a large and handsome species which occurs abundantly in many parts of the British Isles, and it is rather remarkable that up to the present time its zygospores have escaped observation. It is a somewhat variable species with regard to the incisions between the lobes and the form of the lateral lobes. The interlobular incisions may be narrow and closed, or they may be considerably open, and the lateral lobes frequently possess a median rounded protuberance. This is a variation which has received a name from several authors ("var. appendicu- EUASTRUM. / latum Breb." ; "var. majus Rabenh."), but which is not a true variety. Frequently one semicell is typical and the other in possession of this lateral protuberance. Such is the example we have figured on PL XXXIII, fio\ 4. Consult also, West, ' Alg. K Wales/ 1890, p. 287, t. 6, fig. 33. The Desmid to which Bennett gave the name " E. crasso- Jnimeroxum n. var." is a very badly drawn specimen of E. crassum, in which the interlobular incisions were somewhat open. Bennett's idea that it was a hybrid was a mere supposition; he did not even examine the nature of its pro- tuberances or obtain its other views. Var. scrobiculatum Lund. (PI. XXXIII, figs. 7, 8.) E nostrum crassum var. scrobiculatum Lund. Desrn. Suec. 1871, p. 18, t. 2, f. 1 ; Nordst. Norges Desni. 1873, p. 8 ; Be Toni, Syll. Alg. 1889, p. 1088 ; West, Alg. W. Ireland, 1892, p. J 36 ; West & G. S. West, Some N. Ainer. Desni. 1896, p. 242, c. fig. xylogr. ; Alg. S. England, 1897, p. 483 ; Alg. N. Ireland, 1902, p. 27. Cells usually smaller than in the type ; lateral mar- gins of semicells not so hollowed, often straight ; in the centre of the semicells (in the neighbourhood of V o the two small tumours) with 1-6 large scrobiculations, variously disposed ; side view of semicells with more yentricose lateral margins, considerably attenuated towards the apex ; vertical view rather more rectan- gular-oblong than in the type. Length 134-169 /x; breadth 65-88 p. ; breadth of isthmus 18-26 p ; thickness 51-65 JJL. ENGLAND. — Xew Forest, Hants ! SCOTLAND. — Skye, Inverness ! Harris, Lewis, X. Uist, and Benbecula, Outer Hebrides ! WALES. — Moel Siabocl, bog above Capel Curig, bog- between Grlyder Fach and Llugwy, Carnarvonshire ! IRELAND. — Xear G-weedore, near Loughs Grlentornan and Magrath, Donegal ! Cromagloun, Kerry ! Geogr. Distribution. — Germany. Norway. Sweden. Denmark. Poland. Faeroes. United States. West Indies. This is a very characteristic variety of rare occurrence. The scrobiculations in the centre of the semicells, which are the largest marks of that type in any Desmid , vary much in 8 BRITISH PESMIDIACE^. number and in disposition, the commonest arrangements being two (one vertically over the other), and four disposed in the form of a cross. This variability was first pointed out by Nordstedt. The side and vertical views of this variety also differ to a certain extent from those of the type. Var. Taturnii var. nov. (PI. LV, fig. 4.) Cells with a widely-open, acuminate sinus, basal angles of semicells subuncinate-mamillate ; polar lobe aiivil-sliaped with a convex apex, incisions on each side below the polar lobe widely excavated towards their inner extremities ; cell-wall strongly punctate, with a single large scrobiculation in the centre of each semi- cell. Side and vertical views as in the type. Length 165/x,; breadth 110^; breadth of isthmus o ^ O/ JJL. ENGLAND. — Near Salisbury, Wilts! (E. J. Taturri). This variety occurred amongst numerous specimens of the type in a collection from a Sphagnum-bog. The form of E. crassum described by Wood as " E. ornatum' (ride Wood in 'Proc. Acad. Nat. Sci. Pliilad./ 1870, p. 17; 'Freshw. Alg. N. Amer./ 1873, p. 137, t. 21, f. 12), and sub- sequently placed as " E. crassum var. ornatum ' ' by Hansgirg (1888), may possibly be the same as this variety, but neither the description nor the figure given by Wood is sufficiently accurate to determine the identity of the form in question. Note. — E. crassum var. corniibiense Benn. Alg. N. Cornwall, 1887, p. 16, t. 4, f. 19; Cooke, Brit. Desm., 1887, t. 65, f. 4 (from Bennett) ; De Toni, Syll. Alg., 1889, p. 1088. This is a form of E. crassum with open interlobular incisions and with the lateral protuberances on the margins of the lateral lobes, which is most incorrectly described and still more badly figured. " Protuberances" such as those described and figured by Bennett do not occur on any known Euastrum. Moreover, his dimensions are vastly different from the pro- portions of his figure. 3. Euastrum humerosum Ralfs. (PI. XXXIV, figs. 1, 2.) Euastrum humerosum Ealfs, Brit. Desm. 1848, p. 82, t. 13, f. 2 ; Arch, in Pritch. Infus. 1861, p. 729; Eabenh. Flor. Europ. Algar. Ill, 1868, EUASTKUM. 9 p. 182; Wolle, Desm. U. S. 1884, p. 99, t. 28, f. 12-13; Cooke, Brit. Desiu. 1886, p. 66, t. 32, f . 3 ; De Toui, Syll. Alg. 1889, p. 1090 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Eoy. & Biss. Scott. Desiii. 1893, p. 177 ; Nordst. Index Desni. 1896, p. 141 ; West & G. S. West, Alg . S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 61. E. humerosum a. genuinum Eacib. Noun. Desni. Polon. 1885, p. 93. E. pinnatum Balfs b. intermedium Eacib I.e. p. 93, t. 13, f. 4. Hclierella humerosa Kuntze, Eevis. gen. plant. 1891, p. 898. Tells of moderate size, rather less than twice as long as broad, deeply constricted, sinus narrowly linear and dilated at the apex; semicells five-lobed, incisions between the lobes widely open, upper in- cisions deeper and less widely open than lower incisions ; polar lobe dilated, almost anvil- shaped with rounded angles, apex convex, straight, or even slightly retuse, with a fairly deep and narrow median incision ; upper lateral lobes mamillate or narrowly mamillate, directed upwards and outwards ; lower lateral lobes subquadrate, with retuse margins and rounded angles ; semicells with three prominent protuberances across the base and two smaller ones across the middle. Vertical view elliptic, with three prominent protuberances on each side. Cell-wall punctate. Zygospore unknown. Length 1 10-1 23 /x; breadth 65-75 ^ ; breadth of isthmus 15'5— 22 p. ; thickness 40 /x. ENGLAND. — Blea Tarn, Westmoreland ! Pilmoor, N. Yorks ! Xew Forest, Hants (Ralfs). Near Bovey Tracey, Devon (Bennett). Halgavor Moor, Cornwall! WALES. — Llyii Padarn !, Llvn-v-cwm-ffvnon !, and «/ J V f «/ near Bettws-y-coed (Eoy), Carnarvonshire. Dolgelly, Merioneth (Ra Ifs) . SCOTLAND. — Ross ! Inverness, Aberdeen ! Kincar- dine, Forfar, Perth, Argyll, Arran (Eoy fy Bissett). IRELAND. — Lough Guitane and Carrantuohill, Kerry ! Dublin and Wicklow (Archer). Geogr. Distribution. — France. Germany. Austria and Galicia. Xorwav. Sweden. Finland. Poland. t/' Faeroes. India. United States. E. Immerosum is the rarest of the larger British species of Euastrum. It is subject to considerable variation in the 10 BRITISH DESMIDIACEJl. depth of the interlobular incisions, the amount of projection of the upper lateral lobes, and in the shape of the polar lobe. We have given a figure of the form of this species most often observed in Scotland (PI. XXXIV, fig. 1), and it will be seen to differ from the figures given by Ralfs in the convex apex of the polar lobe and in the less deep incisions beneath the polar lobe. All intermediate stages occur between this form and the one figured by Ealfs. Archer (in ' Quart. Journ. Micr. Sci./ 1875, p. 414) observed a zygospore formed by the conjugation of E. humerosum and E. Didelta. This is the only case of true hybridization ever recorded among the Desmidiaceee, and it would have been most interesting to have witnessed the development of the zygospore. Some specimens possess three large scrobiculations situated in the centre of the semicell between the tumours. This form has been named " forma scrobiculata Nordst." 4. Euastrum pinnatum Ralfs. (PI. XXXIV, figs. 3-6.) Euastrum pinnatum Ealfs, Brit. Desm. 1848, p. 81, t. 13, f. 1 ; Arch, in Pritch. Iiifus. 1861, p. 728 ; Eabenh. Flor. Europ. Algar. Ill, 1868, p. 182 ; Lund. Desm. Suec. 1871, p. 19 ; Wolle, Desm. U.S. 1884, p. 98, t. 28, f . 14-16 ; Cooke, Brit. Desm. 1886, p. 66, t. 32, f . 2 ; De Toni, Syll. Alg. 1889, p. 1089 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott. Desni. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 201 ; West & G-. S. West, Alg. N. Ireland, 1902, p. 28. E. pinnatum a. typicum Eacib. Nonn. Desm. Polon. 1885, p. 93. E. multilobatum Benn. Freslrw. Alg. Eng. Lake Distr. 1886, p. 8. t. 1, f. 11 (figure bad). Helierella pinnata Kuntze, Eevis. geii. plant. 1891, p. 899. Cells moderately large, about twice as long as broad, deeply constricted, sinus narrowly linear with the extremity dilated; semicells five-lobed, incisions be- tween the lobes fairly deep and widely open; polar lobe projecting, anvil-shaped with rounded angles, apex straight, rarely retuse or convex, with a fairly deep and narrow median incision ; upper lateral lobes broadly mamillate, with the upper margin horizontal (sometimes much broader, subquadrate, and subemar- ginate) ; lower lateral lobes subquadrate, and retuse with rounded angles ; semicells with a large protu- berance within each of the lower lateral lobes, and with three smaller ones at the base near the centre, EUASTRUM. 11 one just above the isthmus and two others immediately above it, forming a triangle with it ; upper half of semi- cell destitute of protuberances. Side view of semicell with the lower third subrectangular and upper third elongate-pyramidate, protuberances of lower part of semicell showing distinctly at the sides near the base : O i apices dilated, slightly retuse and with rounded angles ; upper lateral lobe widely emarginate. Vertical view elliptic, with four prominent protuberances at each side, and a fifth showing between and below the two central ones ; upper lateral lobes widely emarginate ; polar lobe oblong-rectangular, with retuse sides, emar- ginate poles, and rounded angles. Cell-wall coarsely punctate, angles and protuberances frequently scro- biculate (and with a slightly roughened surface). Zygospore unknown. Length 130-153 p, ; breadth 63-77 JJL ; breadth of isthmus 20-24 /x; thickness 46— 50 /x. ENGLAND. — Angle Tarn, Cumberland ! Elter Water ! , near Bowness (Bissett), Loughrigg (Bennett), West- moreland. Hawkshead, Lancashire ! Xew Forest, Hants (Bennett). WALES. — Capel Curig and Llyn-y-cwni-ffynon !, Pen- y-gwrvd (Ro//), Carnarvonshire. Dolo'elly, Merioneth (Rcdfs). SCOTLAND. — Sutherland ! Ross ! , Aberdeen, Kincar- dine, Forfar, Perth, Argyll (Roij $ Bissett). Lewis, Harris (often abundant), and X. L^ist, Outer Hebrides ! IRELAND.- -Dungloe, Donegal ! Eoundstone, Bally - nahinch, Loughs Aunierin and Shindilla, Galwav ! Xear o «. Castletown and Carrantuohill, Kerry ! Dublin and «, Wicklow (Archer). Geogr. Distribution.- -France. Germany. Galicia in Austria. Xorwav. Sweden. Faeroes. Laiited States. t/ E. pinnatum is a very characteristic species,, and in certain parts of the west of Scotland and Ireland it occurs in abun- dance. The figures given by Ralfs (Lc. t. 13, f. 1) are not good. Ralfs' fig. 1 a gives a correct idea of the outline of the average form, but fie-s. 1 b, c, and d are incorrectlv drawn, Cj •* < > * * *J S 12 BRITISH DESMIDIACE.E. fig". 1 c of the side view being particularly erroneous. Bali's did not grasp the disposition of the protuberances on E. pin- nut urn, causing Lundell ('Desm. Suec/ 1871, p. 19) to mention the typical form as a " forma." The upper half of the semi- cell (in fact, all that part of it above the inferior iiiterlobular incisions) is quite destitute of any trace of protuberances 011 its surface. There is one large protuberance within each lower lateral lobe, and there are three others (not four as figured by Ralfs) in the centre of the basal part of the semi- cell. These three are smaller and disposed in the form of a triangle with one angle immediately above the isthmus. Luii dell was thus quite right in his interpretation of the protuberances on his Swedish specimens. The principal variation met with is in the upper lateral lobes. These lobes are always widely emarginate when seen in either the side or vertical views, but generally inamillate and entire when seen in front view. In some specimens, however, these lobes are very broad in front view (vide PI. XXIV, fig. 6), and they may be rounded-quadrate with ret use margins. Every state is met with between the ordinary mamillate condition and the retuse condition, and the two extremes mav be found on the same cell. These forms t/ with the broad, retuse, upper lateral lobes greatly resemble E. oblongum, but can be at once distinguished in either the side or vertical view. 5. Euastrum oblongum (Grev.) Ralfs. (PL XXXIV, figs. 7-9 ; PL XXXV, fig. 2.) ? ? Euastrum Pecten Ehrenb. Entwick. Lebends. d. Infus. 1832, p. 82 (Description insufficient for identification). Echinella oblonga Grev. in Hook. Brit. Flor. 1833, II, p. 398. Cosmarium sinuosum Corda, Alnianach de Carlsbad, 1835, p. 121, t. 2, f. 21. Micrasterias sinuata Breb. et God. Alg. Falaise, 1835, p. 55, t. 7. Heterocarpella sinuata Breb. in Cheval. microscop. et usage, Paris, 1839, p. 272. Cosmarium oblongum Breb. in Menegh. Synops. Desm. 18-40, p. 221. Eutomia oblonga Harv. Man. Brit. Alg. 1841, p. 188. Euastrum oblongum (Grev.) Ralfs in Ann. Mag. Nat. Hist, xiv, 1844, p. 189, t. 6, f. 4 ;' Hass. Brit. Freshw. Alg. 1845, p. 380, t. 91, f. 1 ; Ralfs, Brit. Desm. 1848, p. 80, t. 12 ; Arch, in Pritch. Infus. 1861, p. 728, t. 3, f. 11 ; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 181 ; Delp. Desm. subalp. 1873, p. 99, t. 6, f. 26-30 ; Kirchn. Alg. Schles. 1878, p. 157; Wolle, Desm. U.S. 1884, p. 98, t. 25, f . 5 (figure bad) ; Cooke, Brit. Desm. 1886, p. 64, t. 31, f . 2 ; Hansg. Prodr. Algenfl. Bohni. 1888, p. 204 ; De Toni, Syll. Alsr. 1889, p. 1086 ; West, Alg. W. Ireland, 1892, p. 136; Alg. Eng. Lake District, 1892, p. 722 ; Roy & Biss. Scott, Desm. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 185 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alcra-fl. Yorks. 1900, p. 61 ; Alg. N. Ireland, 1902, p. 27 ; Scott. Freshw. Plankton, I, 1903, p. 525. EUASTRUM. 13 Euastrutn oblongiforme Cramer in Hechvigia, 1863, p. 64, t. 12, f. 3. Didymidium (Euastrum) oblongum Reinsch, Algenfl. Frankeu, 1867, p. 136. E. oblongum b. oblongiforme (Cram.) Rabenh. Flor. Europ. Algar. Ill, 1868, p. 181; Racib! Nomi. Desm. Polon. 1885, p. 93; De Toni, Syll. Alg. 1889, p. 1087. E. oblongum var. triyibbum Schaarschm. Magyar. Desm. 1882, p. 262, t. 1, f. 2. E. oblongum forma? genuinx (1. typicum ; 2. subcylindricum • 3. elongatum) Racib. Nonn. Desm. Polon. 1885, p. 93. Helierella Pecten Kuntze, Revis. gen. plant. 1891, p. 897. Cells large, about twice as long as broad, in general outline oblong-elliptic, deeply constricted, sinus nar- rowly linear and slightly dilated at the apex; semicells five-lobed, incisions between the lobes fairly deep and generally slightly open (upper ones occasionally closed) ; polar lobe widely cuneate, with rounded angles, apex convex with a deep and narrow median incision; upper and lower lateral lobes similar, upper ones slightly smaller than lower ones, subquadrate with retuse mar- gins and rounded angles; semicells with a protuberance within each of the lateral lobes, with one at the base immediately above the isthmus, and with two smaller ones in the centre (often with a large scrobiculation between them). Side view of semicell elongate-pyra- midate, with rectangular basal angles and a dilated, " o o convex apex ; lateral lobes rotund-rhomboidal, with somewhat retuse margins, upper angle of upper lateral ]obe rarelv emaroinate. Vertical view broadly elliptic, «/ «,' poles narrow and rounded, sides with four protuber- ances and a fifth one between and beneath the two central ones ; polar lobe oblong elliptical, with convex sides, emarginate poles, and rounded angles. Cell- wall finely punctate. Zygospore globose, closely covered with numerous mamillate projections. Length 144-205 p, ; breadth 74-107 /x; breadth of isthmus 20-3 1 /x ; thickness 46-65 /x ; cliam. zygosp. without mamillate projections 92-123 /x ; length of mamillas 7*5-9 /x. ENGLAND. — Cumberland \ Westmoreland !, (Ealfs). AY., X. and E. Yorks. (zygospores from Pilmoor, N". Yorks) ! Lancashire ! Cheshire (Rolfs). Leicestershire 14 BRITISH DESMIDIACE^:. (Roy). Essex! Warwick (Wills). Surrey! (Ralfs). Sussex (Ralfs). Hants. ! (Ralfs). Devon! Cornwall! WALES.- -Fairly general ! SCOTLAND. — General ! (Roy $ Bissett). Zygospores from Powlair, Aberdeen (Roy fy Bissett). Outer Hebrides ! Orkneys ! Shetland s ! IRELAND. — Donegal ! Mayo ! Gal way ! Kerry ! Dublin and Wicklow (Archer). Zygospore from Carrick Mountain, Wicklow (Archer). Down! Londonderry! Geogr. Distribution.- -France. Germany. Austria (var.) and Galicia. Hungary. Italy. Norway. Sweden. Denmark. Bornliolm. Finland. Poland. ]SL, Central, and S. Russia, Faeroes. Greenland. Japan. United States. Brazil. This is a large and handsome Desmid which is generally distributed throughout the British Islands. The figures given by Ralfs are not very accurate except for the outline. That author failed to depict the two small, central protuberances in each semicell, and his vertical view is very erroneous. Between and slightly below these central protuberances a large scro- biculation is frequently present ; this form has been named " forma scrobiculata Nordst." There are no protuberances on the front surface of the polar lobe such as are indicated by Ralfs and other observers. This is seen at once from the vertical view. The protuberances figured by Ralfs and others on the polar lobes of many species of this genus are frequently due to the refraction caused by the vertical emarginatioii of each side of the polar lobe. Var. cephalophorum West, (PI. XXXV, fig. 1.) E. oblongum Wolle, Desni. U.S. 1884, t. 25, f. 6. E. oblongum (Grev.) Ealfs var. cephalophorum West, New Brit. Freshw. Alg. ]S94, p. 4 ; Roy & Biss. Scott. Desni. 1894, p. 255. A variety with the lower interlobular incisions widely open, and the upper interlobular incisions narrowly linear ; upper lateral lobes much smaller than the lower lateral lobes. Length loo/*,; breadth 90 /x; breadth of isthmus /*. SCOTLAND. — Near the Spittal of Glen Shee, Perth ! EUASTRUM. 1 5 Var. depauperatum r»r. nov. (PI. XXXIV, fig. 10.) A variety with the interlobular incisions very shallow f »/ and widely open ; polar lobe more rounded and lateral lobes very short. e/ Length 140 JJL ; breadth Go /u, ; breadth of isthmus 17ft. IRELAND. — Xear Glenties, Donegal! ' O "\Ve mentioned the occurrence of this form in the ' Alg. of N. Ireland/ 1902, p. 27. Note. — E. ol)longum var. integrum Benn. Alg. N. Cornwall, 1887, p. 16, t, 4, f. 18-; Cooke, Brit. Desm. 1887, t. 66, f. 1 (from Bennett) ; De Toiii, Syll. Algar. 1889, p. 1088. Bennett's description of this form together with his bad figure make future identification of it impossible. The " protuberances ' he mentions are such as are not found in any Eiiastrum of this group; neither is any form of E. oblongum known in which the polar lobe is entire. (Consult remarks under " E. crassum var. cornubiense" p. 8.) G. Euastrum Didelta (Turp.) Ralfs. (PL XXXV. figs. 3-7.) ? ? Heterocarpella Didelta Turp. Aper^ti organograph. 1828, p. 315, t. 13, f. 16. ?? Cosmarium fenestratum Corda, Almanach de Carlsbad, 1839, p. 243, t. 5, f . 29. Cosmarium Didelta ]\Ienegh. Syiiops. Desm. 1840, p. 219; Kiitz. Spec. Alg. 1849, p. 174. Euastrum Didelta (Turp.) Ealfs in Ann. Mag. Xat. Hist, xiv, 1844, p. 190, t. 7, f . 2 a and 6 only ; Hass. Brit. Freshw. Alg. 1845, p. 381, t. 90, f. 8 ; t. 91, f. 11 ; Ealfs, Brit. Desm. 1848, p. 84, t. 14, f. 1 ; Arch, in Pritch, Infus. 1861, p. 729, t. 1, f. 23-25 ; t. 3, f. 61 ; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 184 ; Delp. Desm. subalp. 1873, p. 105, t. 6, f . 2 ; Kirchn. Alg. Schles. 1878, p. 157 ; Wolle, Desm. U.S. 1884, p. 99, t, 29. f . 9-10 ; Cooke, Brit. Desm. 1886, p. 69, t. 34, f . 1 ; Hansg. Prodr. Algenfl. Bohni. 1888, p. 205 ; De Toni, Syll. Alg. 1889, p. 1093 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng" Lake Distr. 1892, p. 723 ; Roy & Biss. Scott. Desm. 1893, p. 176 ; Xordst. Index Desm. 1896, p. 106"; West & G. S. West, Alg. S. England, 1897, p. 483 ; G. S. West, Varia- tions Desm. 1899, p. 382, t. 8, f. 13-19 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 61 ; Alg. N. Ireland, 1902, p. 28. E. Didelta var. sinuatvm Gay, Monogr. loc. Conj. 1884, p. 56, t. 1, f. 11. E. Didelta a. typicum Racib. Xonn. Desm. Polon. 1885, p. 92. E. Didelta b. tatricum Racib. I.e. t. 13, f. 3. Helierellafenestrata Kuntze, Revis. gen. plant. 1891, p. 898. Cells moderately lars^e, twice or rather more than t/ O twice as long as broad, deeply constricted, sinus 16 BRITISH DESMIDIACE^:. narrowly linear with a dilated extremity ; semicells pyramidate with a truncate apex and sinuate margins, sometimes almost five-lobed ; basal angles broadly rounded, rounded-rectangular, or even ret use ; lateral margins with two hollows, sometimes slight and some- times fairly deep, often unequal ; apical part of cell standing out as a polar lobe, subtruncate at the apex with rounded angles, and with a deep linear incision in the middle ; semicells with three protuberances across the base and two across the middle. Side view of semi- cell elongate-pyramidate, basal angles subrectangular, somewhat wider above the base, then tapering upwards to the apex, which is truncate with rounded angles. Vertical view elliptical, with three protuberances on each side, the two upper protuberances which show in the middle of the lateral margin alternating with the three lower ones ; polar lobe broadly elliptic. Cell- wall punctate. Zygospore globose, furnished with numerous, blunt, somewhat curved papillae. Length 130-195 /x; breadth 70-91^; breadth of isthmus 16-27 ft ; thickness 42— 45 /A; diam. zygosp. without papillae 73'6-86/u,; length of papillae 9-13 p. ENGLAND. — Cumberland ! Westmoreland (at 2,400 ft. on Helvellyn) ! (Rolfs). W. and X. Yorks ! Lancashire (zygospores from near Wrynose) ! Leicestershire (Roii). Wilts ! Warwick (Wills). Surrey ! Sussex (Rolfs); Kent ! (Rolfs). Hants ! (Rolfs}. Devon ! (Bennett). Cornwall! (Rolfs). WALES. — Fairly general ! SCOTLAND ! General ! (Roy $ Bissett). Zygospores at Dalwhing near Aboyne, Aberdeen (Roy § Bi-ssett). Common in Outer Hebrides ! Orkneys ! e/ IRELAND. — Donegal ! Mayo ! Gal way ! Kerry ! Dublin and Wicklow (Archer). Zygospores from Carrick Mountain (A rclter). Down! Londonderry! Geogr. Distribution. — France. Germany. Austria and Galicia. Italy. Norway. Sweden. Denmark. Bornholm. Finland. Poland (var). X. and S. Russia. EUASTEUM. 17 Faeroes. Greenland. India. Ceylon. Azores. United t/ States. Paraguay. This is one of the most abundant of the laro-e British o species of Euastrum, and is subject to considerable variation in outward form. The sinuation of the lateral margins of the semicells varies very much, even in the semicells of the same plant. The form named " var. sinuatum ' ' by G-ay has there- fore no claim to rank as a distinct variety. The form named " var. tatricum" by Eaciborski is based on an error in Ralfs' ' British Desmids.1 This is another species in which Ralfs failed to depict the surface protuberances correctly. The only protuberances on the semicell of any specimen of E. Didelta are three across the base, the middle one beino- ' ~ immediately above the isthmus, and two across the centre. Monstrosities of this Desmid are not uncommon ; they have been figured by Archer in ' Proc. Dubl. Nat. Hist. Soc./ 1859, p. 208, t. 1, f. 12; ' Nat. Hist. Rev./ 1859, vi, p. 470, t, 33 ; by Bulnheim in ' Hewidgia/ 1861, p. 52, t. 9, f. 6; and by West & G. S. West in ' Ann. Bot,/ xii, 1898, t. iv, f. 39. Some specimens possess a large scrobiculation beneath the two central protuberances ; this form has been named " forma scrobiculata Nordst.," and is fairly general in its distribution. 7. Euastrum affine Ralfs. (PL XXXV, figs. 11,12.) Euastrum affine Ealfs in Ann. Mag. N"at. Hist, xiv, 1844, p. 191, t. 7, f. 3 ; Hass. Brit. Freshw. Alg. 1845, p. 382, t. 90, f . 9 ; Kalfs Brit. Desm. 1848, p. 82, t. 13, f. 3; Arch, in Pritch. Infus. 1861, p. 729 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 182 ; Cooke, Brit. Desm. 1886, p. 67, t. 33, f . 2 ; De Toni, Syll. Alg. 1889, p. 1091 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott, Desm. 1893, p. 175; Xordst. Index Desm. 1896, p. 40; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 61 ; Alg. N. Ireland, 1902, p. 28. Helierella affinis Kuntze, Eevis. gen. plant. 1891, p. 898. Cells of medium size, somewhat less than twice as long as broad, very deeply constricted, sinus narrowly linear with a dilated extremity ; semicells three-lobecl with two intermediate lobules, sinuses between the lobes and the lobules deep and widely open ; polar lobe outstanding, anvil-shaped, with rounded angles and a convex apex, and with a median linear notch of some 2 18 BRITISH DESMIDIACE^]. depth ; lateral lobes subquadrate, with rounded angles and retuse sides ; intermediate lobules mamillate and prominent ; semicells with a large protuberance within each lateral lobe, and with four in the centre, two small ones immediately above the isthmus, and two larger ones immediately above them. Side view of semicell subquadrate in the lower half, with retuse sides ; upper half pyramidate, with deeply retuse sides and a dilated, rounded-truncate apex ; intermediate lobule emar- ginate ; lateral lobes (at base) rhomboidal, with rounded angles and retuse sides. Vertical view elliptic, with four prominent protuberances along each side ; inter- mediate lobules emarginate ; polar lobe quadrate- oblong, sides slightly convex, poles deeply emarginate. Cell-wall punctate. Zygospore unknown. Length 98-117^; breadth 53-64 //,; breadth of isthmus 17-18 /A; thickness 35-38 {JL. ENGLAND. — Cumberland ! Westmoreland ! (Ralfs) . W. and N". Yorks ! Lancashire ! Surrey ! Sussex (Rolfs). Hants. (Ralfs). Wilts! (Tat urn). Devon! (Bennett). Cornwall (Marquand). WALES. — General in Carnarvonshire (Glyder Fach at 2,200 ft.) ! Dolgelly, Merioneth (Ralfs). SCOTLAND. — General, but not abundant ! (Roy fy Bissett). Outer Hebrides ! IRELAND. - - Donegal ! Mayo ! Gal way ! Kerry ! Dublin and Wicklow (Archer). Geogr. Distribution. — France. Germany. Norwa}^. Sweden. Denmark. X. Russia, India. United States. E. affine is a very characteristic species and cannot be easily confused with any other. The disposition of the surface protuberances and the form of the polar lobe at once dis- tinguish it from E. Didelta. It often occurs in quantity in upland Sphagnum-bo gSj and is not infrequently associated with E. ampullaceum. Nordstedt has described a " forma scrobiculata" of it/ with a conspicuous central scrobiculation, hut we have not observed this form from Britain. EUASTRUM. 19 8. Euastrum ampullaceum Ralfs. (PI. XXXV, figs. 8-10.) «nii».i.Un<:t'iirii Ralfs, Brit. Desni. 1848, p. 83, t. 13, f. 4 (Euastrum without name figured in Hass. Brit. FresliAv. Alg. 1845, t. 90, f. 11) ; Arch, in Pritch. Infus. 1861, p. 729; Rabenh. Flor. Europ. Algar III, 1868, p. 183 ; Delp. Desin. siibalp. 1873, p. 104, t. 6, f. 3, 4; Kirchn. Alg. Schles. 1878, p. 158 ; Cooke, Brit. Desm. 1886, p. 68, t. 33, f. 3 ; Hansg. Prodr. Alo-enfl. Bohm. 1888, p. 205 ; De Toni, Syll. Alg. 1889, p. 1091 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 722 : Roy & Biss. Scott Desin. 1893, p. 175 ; Nordst. Index Desm. 1896, p. 44; West & G-. S. West, Alg. S. England, 1897, p. 483; Alga-fl. Yorks. 1900, p. 61 ; Alg. N. Ireland, 1902, p. 28. E. ampullaceum forma scrobiculata Nordst. Norges Desm. 1873, p. 8. Helierella ampullacea Kuntze, Revis. gen. plant. 1891, p. 898. Cells of medium size, a little more than 1-J- times longer than broad, very deeply constricted, sinus narrowly linear and dilated at the extremity; semi- cells three-lobed ; polar lobe cuneate and dilated, with rounded angles, apex convex with a deep and narrow median incision ; lateral lobes much larger than the polar lobe, triangular with rounded basal angles, superior margin of the lobes with a mamillate projection, which is sometimes reduced to a rounded elevation ; semicells with three protuberances across the base, the median one being emarginate, and with two across the centre, also with three conspicuous scrobiculations dis- posed between the five protuberances. Side view of semicell elongate-pyramidate, basal angles rectangular I i/ 7 _ O O and basal part of margins slightly retuse, upper part of margins somewhat concave, apex rounded. Vertical view pointed-elliptic, with four protuberances on each side and a fifth between and beneath the two central ones ; mamillate projection of lateral lobes widely emarginate ; polar lobe rectangular, with subacute angles and retuse sides. Cell-wall finely scrobiculate. Zygospore globose or ovoid-globose, ornamented with numerous mamillate projections. Length 93-110/x; breadth 57-59 /i ; breadth of isthmus 14-17*5^; thickness 34-36 ft; diam. zygosp. without mamillate projections 54-72 {JL ; length of mamillae 5— 6'4 p. ENGLAND.- -Cumberland ! Westmoreland! (Ralfs). 20 BRITISH W. and N. Yorks ! Lancashire ! Surrey ! Sussex (Rolfs). Kent (Ralfs). Hants! (Rolfs}. Devon! (Bennett). Wilts! Cornwall! WALES. — General through Carnarvonsliire (Glycler Fach at 2,200 ft.) ! Dolgelly, Merioneth (Ralfs). SCOTLAND. — Sutherland ! , Ross ! , Inverness ! , Aber- deen ! , Kincardine ! , Forfar ! , Perth ! , Argyle, Arran, Fife ; zygospores near Cambus-o'-May, Aberdeen (Roy Sf Bissett). Skye (with zygospores) ! Common in Outer Hebrides ! Orkneys ! f,' IRELAND. — Donegal ! Gal way ! Mayo ! Kerry ! Dublin and Wicklow (Archer). Down ! Antrim ! Geogr. Distribution. — France. Germany. Hungary. Italy. Norway. Sweden. S. Russia. Faeroes. India (var.). United States. This species is generally distributed throughout the Sphagnum-bogs of the British Islands. The general outline in front view and the form of the polar lobe, particularly in the vertical view, are absolutely characteristic. We have ' V examined many thousands of British specimens, and find the three scrobiculations in the centre of the semi-cells very con- stant, this being the reason we have included Kordstedt's "forma scrobiculata ' with the type form. Ealfs did not accurately indicate the surface protuberances,, and he remarks in his text that thev were " indistinct/ 9. Euastrum sinuosum Lenorm. (PI. XXXVI, fig. 1.) Euastrum sinuosum "Lenormand, in herb." Ralfs, Brit. Desni. 1848,. p. 85 ; Lund. Desni. Suec. 1871, p. 20; Nordst. Alg. aq. dulc. et Char. Sandvic. 1878, p. 14; Cooke, Brit. Desni. 1886, p. 71, t. 34, f. 3 ; Nordst. Freshw. Alg. N. Zeal. 1888, p. 33 ; De Toni, Syll. Alg. 1889, p. 1098 ; Borg. Desni. Brasil. 1890, p. 33, t, 3, f. 16 ; West, Alg. W. Ireland, 1892, p. 138 ; Alg. Eng. Lake Distr. 1892, p. 723 ; Roy & Biss. Scott. Desni. 1894, p. 178; Nordst. Index Desm. 1896, p. 235"; West & GK S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 61 ; Freshw. Chlorophy. Koh Chang, 1901, p. 168; Alg. N. Ireland, 1902, p. 28; Freshw. Alg. Ceylon, 1902, p. 148. Euastrum circulate Hass. var. /3 Kalfs, Brit. Desm. 1848, p. 85, t. 13, f . 5 a,. b, and d. E. circulare C. Falesiensis Breb. Liste Desm. 1856, p. 122 (Ralfs, Brit. Desm. t. 14, f . 3 b and c). E. circulare /3 sinuosum Hansg. Prodr. Algenfl. Bohm. 1888, p. 206. Helierella sinuosa Kiintze, Revis. gen. plant. 1891, p. 899. EUASTRUM. 21 Cells small, about If times longer than broad, deeply constricted, sinus narrowly linear with a dilated extre- mity ; semicells three-lobed ; polar lobe prominent and outstanding, quadrate-cuneate, angles rounded, apex truncate with a narrow median incision of some depth ; lateral lobes bilobulate, lobules rounded, separated by a widely-open sinus, the upper one not projecting so far out as the lower ; semicells with three protuberances across the base and two across the centre. Side view of semicell pyramidate with a quadrate base, upper part of lateral margins slightly retuse, apex rounded- truncate. Vertical view elliptic, with three protube- rances on each side, and the two central ones showing above and between them ; polar lobe oblong-rect- angular, poles retuso-emarginate. Cell-wall finely punctate, puiictulations often scarcely visible. Zygospore unknown. Length 56-78 ^ ; breadth 35-46 ^ ; breadth of isthmus 9-15 \L ; thickness 21-30 /*. ENGLAND. — Cumberland ! Westmoreland ! (BaJfs). W. and X. Yorks ! Lancashire ! Surrey ! Hants ! (Ralfs). Devon! WALES. — Capel Curig, Snowdon, and Llyn-y-cwm- ifynon, Carnarvonshire ! SCOTLAND. — General, but rare (Roy $• Bissett). Rhi- conich and Loch Gulag1. Sutherland ! L. Luichart, o ? ' Ross ! Outer Hebrides ! Shetlands ! IRELAND. — Donegal ! Galway ! Kerry ! Dublin and Wicklow (Archer). (reoc/i'. Distribution. — France. Germany. Austria and Galicia. Italy. Xorway. Sweden. Denmark. Poland. S. Russia. Faeroes. India. Ceylon (var.). Siam. Singapore. Java. Australia. Xew Zealand. Central Africa. Sandwich Islands. United States. Guiana. Brazil. Much confusion has existed concerning the nomenclature of this characteristic Euastrum. It has been referred by many authors to "Euastrum circulars Hass." as a variety, but the latter species does not exist, HassalFs figure being 22 BRITISH DESMIPIACE/E. most probably a very erroneous drawing of Euastrum ansa- tum Ralfs. It is a variable species with regard to the depth of the sinuatioiis of the margins,, and for this reason we have included " var. Falesiensis Breb." as part of the type. The five protuberances,, three basal and two central, some- times each possess a conspicuous central scrobiculation, and rarely, similar scrobiculations are found between the pro- tuberances. The zygospore of E. sinuosum var. simplex Mask, has been described and figured as " globose, with simple stout spines." Consult Maskell, ' Further Notes New Zeal. Desm/ 1888, p. 11, t. 1, f. 6. Var. reductum West & G. S. West. (PL XXXVI, %s. 2, 3.) E. sinuosum var. reductum West &• G. S. West, Welw. Afrie. Freshw. Alg. 1897, p. 83 ; Desm. Singapore, 1897, p. 160, t. 8, f . 17 ; Freshw. Alg. Ceylon, 1902, p. 148. Cells somewhat smaller than in the type, polar lobe not dilated, lateral lobules less prominent ; in vertical view protuberances considerably reduced, and polar lobe quadrate-oblong without emarginate poles. Length 46-59 /x; breadth 24-32 go /A ; breadth of isthmus 7'5-9'5 /x ; thickness 15-18/x. EXGLAXD.- -Thursley Common, Surrey ! IRELAND. — Ballvnahinch, Galway ! I V Geogr. Distribution. — Ceylon. Singapore. T\T. Africa. 10. Euastrum Jenneri Arch. (PL XXXVI, fig. 4.) Euastrum circulare var. j Ralfs, Brit. Desm. 1848, p. 85, t. 13, f. 5 c. E. circulare var. Ralfsii Breb. Liste Desm. 1856, p. 122 ; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 183 ; Cooke, Brit. Desm. 1886, p. 72, t, 34, f . 4 ; Nordst. Index Desm. 1896, p. 150 ; West & G. S. West. Alga-fl. Yorks. 1900, p. 62. E. Jenneri Arch, in Pritch. Infus. 1861, p. 730. This species differs from E. sinuosum in the broader polar lobes; in the larger lateral lobes, which are more quadrate, with equal lobules ; and in the surface protuberances, of which there are eleven, a basal row EUASTBUM. 23 of four, a median row of three, then a row of four across the upper part of the lateral lobes. Cell-wall punctate. Zygospore unknown. Length 72 /x ; breadth 45 /x ; breadth of isthmus 15 p.. EXGLAXD. — Westmoreland (Rolfs). Strensall Com- mon, X. Yorks ! IRELAXD. — Ballvnahinch, G-alwav ! i ^ «.' Geogr. Distribution. — France. United States. We have only seen this Desmid on two occasions and have not vet succeeded in obtaining side or vertical views. It t may only be a variety of E. sinuosum, but this point cannot well be decided until the other views have been obtained. 11. Euastrum aboense Elfv. (PI. XXXVI, figs 5, 6.) Euastrum aboense Elfv. Anteck. Finska Desm. 1881, p. 7, t. 1, f. 2 ; De Toni, Syll. Alg. 1889, p. 1103 ; Boy & Biss. Scott, Desm. 1894, p. 175 ; Kordst. Index Desm. 1896, p. 36 ; West & G. S. West, Notes Alg. Ill, 1903. E. inerme (Ealfs) Lund. var. aboense Eacib. Xonn. Desm. Poloii. 1885, p. 92. Helierella aboensis Kuntze, Bevis. gen. plant. 1891, p. 898. Cells small, about 14- times longer than broad, very deeply constricted, sinus narrowly linear with a slightly-dilated extremity ; semicells pyramidate- rounded (faintly subrect angular), lateral margins sin- uate, with two shallow hollows and a somewhat broad rounded projection in between ; apex subtruncate with rounded angles and a narrow median incision ; semi- cells with a slight depressed protuberance above the isthmus and two others across the centre, also with 11-13 conspicuous scrobiculations disposed more or less in a regular pattern across the broad part of the semicell. Side view of semicells quadrate at the base, with rounded angles and retuse sides ; upper portion shortly pyramidate with a rounded-truncate apex. Vertical view elliptic, with two slight protuberances in the middle of each side. Zygospore unknown. 24 BRITISH DESMIDIACE^. Length 58-65 /x ; breadth 37-42 //, ; breadth of isthmus 11 '5-1 3 p. ; thickness 24-25 p.. WALES. — Capel Curig, and Llyn-y-cwm-ffynon, Car- narvonshire ! SCOTLAND. — On Ben Mulch Dhui, near Loch Etcha- chan, Aberdeen (Roy fy Bissett). Geogr . Dis trib i itioi i . — Finlan d . E. aboense differs from E. inerme in its slightly larger size, in the relatively greater width of the semicells, in the rounded basal angles, and in the scrobiculations on the front of the semicells. The small thickened protuberance which is situated just above the isthmus in the semicells of E. inerme, is repre- sented by a very slight protuberance in E. aboense. The side and vertical views also differ slightly. It is a species rarely met with. 12. Euastrum inerme (Ralfs) Lund. (PL XXXVI, figs. 7, 8.) Euastrum elegans j3 inerme Kalfs, Brit. Desm. 1848, p. 89, t. 14, f . 7 e ; Eabenh. Flor. Eiirop. Algar. Ill, 1868, p. 186 ; Kirchn. Alg. Schles. 1878, p. 159 ; Hausg. Prodr. Algenfl. Bohm. 1888, p. 207. Euastrum inerme Lund. Desm. Suec. 1871, p. 20, t. 2, f . 3 ; Cooke, Brit. Desm. 1886, p. 75, t. 35, f . 4 ; De Toni, Syll. Alg. 1889, p. 1103 ; West, Alg. W. Ireland, 1892, p. 139 ; Eoy & Biss. Scott. Desm. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 146 ; West & G. S. West, Alg. S. England, 1897, p. 484 ; Alg. N. Ireland, 1902, p. 29. E. inerme a. Ralfsii Racib. Nonn. Desm. Polon. 1885, p. 92. E. inerme c. Lundellii Kacib. I.e. Helierella inermis Kuntze, Eevis. gen. plant. 1891, p. 898. Cells small, subelliptic in outline, about If times longer than broad, very deeply constricted, sinus nar- rowly linear with a slightly-dilated extremity ; semi- cells subpyramidate, basal angles obliquely truncate so that the widest part of the semicell is above the base ; lateral margins with two slight hollows, having a broad, rounded projection between ; apex slightly protracted, truncate, with a deep and narrow median notch; semi- cells with a small thickened protuberance in the middle immediately above the isthmus, having two small pro- tuberances across the centre and a large scrobiculation between them. Side view of semicell pyramidate with a subquadrate base ; lateral margins slightly retuse EUASTRUM. 25 near the base and also towards the apex, with a scrobiculatioii showing at the middle of the margin on each side ; basal angles of semicell quadrate. Vertical view elliptic, with two protuberances on each side, and a third smaller one showing between and beneath them ; also with the scrobiculation between the central protuberances on each side. Cell-wall very finely punctate. Zygospore unknown. Length 50-02 //, ; breadth 30-40 ^ ; breadth of isth- mus 7'5-13/x; thickness 20-23*5^. ENGLAND. — Loughrigg, Westmoreland (Bennett). Thursley Common, Surrey ! Dartmoor, Devon ! SCOTLAND. — Sutherland ! , Eoss ! , Inverness ! , Aber- deen ! , Kincardine, Forfar, Perth ! , Argyll, Arran (Pi oij §• Bis sett). Often abundant in the Outer Hebrides ! IRELAND. — Loughs Cloffher and Machuffh. and near ~ o o ' Glenties, Donegal ! Ballynahinch, Loughs Athry, Aunierin, and Derryclare, Gralway ! Glengariff, Adrigole, and Castletown, Kerry ! Geoor. Distribution. — Germany. Austria and Galicia. v Italy. Norway. Sweden. Denmark. Poland. S. Russia. Faeroes. United States. E. inerme is a rare species in England and Wales, but often occurs in great abundance in the west of Scotland, the Outer Hebrides, and the west of Ireland. In these situations it is frequently associated with large numbers of E. ventricosum. It is a species of definite and constant shape, with very characteristic markings, and it cannot well be mistaken for any other British species of the genus. Ealfs was greatly in error in associating it with Euastrum elegans, a species with which it has no close affinity. i/ 13. Euastrum cuneatum Jenner. (PL XXXVI, fig. 9.) Euastrum cuneatum Jenner in Ealfs' Brit. Desrn. 1848, p. 90, t. 32, f . 3 a ; Arch, in Pritch. Infus. 1861, p. 931 ; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 187 (formae a et 6) ; Xordst. Norses Desm. 1873, p. 9 ; Cooke. Brit. Desm. 1886, p. 76, t. 34, f. 6 : Wolle, Freshw. Alg. U.S. 1887, p. 3") t. 58, f. 12, 13 ; West, Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 723; Roy & Biss. Scott. Desm. 1893, p.' 176; Nordst. 26 BRITISH DESMIDIACE^;. Index Desm. 1896, p. 93 ; West & GK S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 62 ; Alg. X. Ireland, 1902, p. 28. Helierella cuneata Kuntze, Eevis. gen. plant. 1891, p. 898. Euastrum cuneatum forma punctata Schmidle, Beitr. Algenfl. Rheineb. 11. Schwarzwald, 1895, p. 80. Cells moderately large, more than twice as long as broad, deeply constricted, sinus narrowly linear with the extremity dilated; semicells narrowly pyramidate, basal anoies slightly rounded and often a little thick- o o «/ ened, lateral margins almost straight (generally faintly sinuate), apical angles slightly rounded, apex truncate with a narrow and fairly-deep median incision ; semi- cells without protuberances, or with a very slight swelling within each basal angle. Side view of semi- cell ovate-pyramidate, apex truncately rounded. Ver- tical view broadly elliptic, lateral margins convex or very slightly triundulate, Cell- wall finely scrobiculate. Zygospore unknown. Length 96-128 /x; breadth 47-59 /x ; breadth of isthmus 13-22 ft; thickness 42 /x. ENGLAND.- -Cumberland ! Westmoreland! (Bissett). W. and X. Yorks ! Lancashire ! Surrey ! Sussex (Rolfs). Hants (Bennett). . — General throuhout Carnarvonshire ! Ffes- tiniog !, and Dolgelly (Ralfs), Merioneth. SCOTLAND. — Sutherland, Ross, Inverness, Aberdeen ! , Kincardine, Forfar, Perth ! , Dumfriesshire (Roy $ Bissett). Kirkcudbright ! Outer Hebrides ! IRELAND. — Near Loughs Glentornan and Macgrath, Donegal ! Jar Connaught and near Oughterard, Galway ! Carrantuohill, Kerry ! Dublin and Wicklow, (Arclier). Lough Fea, Londonderry ! Geofj-r. Distribution.- -France. Germany. Galicia in Austria. Norway. Sweden. X. Eussia. Greenland. Australia. Xew Zealand (var.). United States. This characteristic species is often abundant amongst sub- merged Sphagnum in association with E. ampullaceum, Cos- marium Oucurbita, Micrasterias tr-nncata, Eremosphserq viridis, and other Alga?. We do not know of any near relatives to E. cuneatum. The broadly-truncate apices, pyramidate semi- cells, and absence of protuberances are all peculiar features. EUASTRI'M. 27 The basal view of tlie semicell given by Halt's (I.e. t. 32, f. ob) is incorrect. We have examined hundreds of specimens of this species and the vertical view is broadly elliptic, occasionally exhibiting' the merest trace of three undulations along each side. 14. Euastrum ansatum Ralfs. (PI. XXXVI, figs. 10-13.) ': E vast rum circulare Hass. Brit. Freshw. Alg. 1845, p. 383, t. 90, f. 5 (figure bad) ; Ralfs, Brit. Desm. 1848, p. 85, t. 14, f. 3 a (from Hassall) ; Arch, in Pritch. Infus. 1861, p. 729; Cooke, Brit. Desm. 1886, p. 71. t. 34, f. 2 (from Hassall or Ralfs) ; De Toni, Syll. Alg. 1889, p. 1097 ; West, Alg. W. Ireland, 1892, p. 138 ; Alg. Eng/Lake Distr. 1892, p. 723. E. ansatum Ralfs, Brit. Desm. 1848, p. 85, t. 14, f. 2 [Not E. ansatum Ehrenb., 1832, which is Cosmarium ansatum (Ehrenb.) Rabenh.1 : Arch. in Pritch. Infus. 1861, p. 729 ; Lund. Desm. Suec. 1871, p. 20 ; "Kirclm. Alg. Schles. 1878, p. 158 ; Cooke, Brit. Desm. 1886, p. 70, t. 33, f . 5 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 206 ; De Toni, Syll. Alg. 1889, p. 1096; West, Alg. W. Ireland, 1&92, p. 138; Roy A: Biss. Scott. Desm. 1893, p. 176; Nordst. Index Desm. 1896, p. 46;* West & G. S. West, Alg. S. England, 1897, p. 483; Alga-fl. Yorks. 1900, p. 62; Alg. N. Ireland, 1902, p. 28 ; Scott. Freshw. Plankton, I, 1903, p. 525. Cosmarium circulare Kiitz. Spec. Alg. 1849, p. 174. Euastrum circulare D. Hassallii Breb. Liste Desm. 1856, p. 122. Didymidium (Euastrum) ansatum Reinsch, Algenfl. Fraiiken, 1867, p. 130. Euastrum Ral/sii Rabenh. Flor. Europ. Algar. Ill, 1868, p. 184. E. ansatum var. sublobatum Delp. Desm. subalp. 1873, p. 103, t. 6, f. 35-36. Helierella circularis Kuntze, Revis. gen. plant, 1891, p. 898. H. ansata Kuntze, I.e. Cells somewhat small, about twice as long as broad, deeply constricted, sinus narrowly linear with a dilated extremity ; semicells pyramidate with a broad base, basal angles rounded, lower part of lateral margins convex with a slight undulation above the basal angles, upper part of margins concave, apex rotundo-truncate, with a narrow and fairly deep median incision; semi- cells with a slight protuberance immediately above the isthmus and two rather larger ones across the centre. Side view of semicell elongate-pyramidate, with a pro- tuberance just above the base on each side, upper part of margins concave, apex rounded. Vertical view elliptic, poles broadly triangular with rounded angles ; with two protuberances in the middle on each side, and a third one between and beneath them ; polar lobe broadly elliptic-oblong. Cell-wall punctate, punctula- tions in vertical lines. 28 BRITISH DESMIDIACE^. Zygospore globose, ornamented with numerous bluntly-rounded (or abruptly-sharp-pointed) spines. Length 70-91 p.; breadth 32-47 /*; breadth of isth- mus 12-1 5 ft; thickness 26-29 /x; diam. zygosp. with- out papilla 38'4-55'5ft; length of papillae 5-6*4 JJL. ENGLAND. — Cumberland ! Westmoreland! (Ealfs). W., N., and E. Yorks ! Lancashire ! (ttalfs). Cheshire (Rolfs). Leicestershire (Roy). Warwickshire (Wills). Gloucestershire (Rolfs). Surrey ! (Ealfs). Sussex (Rolfs). Kent! Hants! (Rolfs). Devon! (Bennett). Cornwall! (Ralfs). WALES. — General and abundant (at 2,200ft. on Glyder Fach, Carnarvonshire) ! IRELAND. — General ! SCOTLAND. — General and abundant ! (Roy fy Bissett). Outer Hebrides ! Orkneys ! Shetlands ! Often in the plankton ! Geogr. Distribution. — France. Belgium. Germany. Austria and Galicia. Hungary. Italy. Norway. Sweden. Denmark. Bornholm. Finland. N. and S. Russia. Faeroes. Iceland. Greenland. Central China. Japan. India. Ceylon. Burmah (var.) Siam. Singapore. Sumatra. Java. Australia (form). New Zealand. Madagascar. E. Africa. Azores. Sandwich Islands. United States. W. Indies (var). Brazil. Paraguay. E. ansatum is one of the most generally distributed of the British species of the genus. The " Euastrum ansatum } described by Ehrenberg in 1832 is a Cosmarium which is now known to occur in several parts of the world. The " Euastrum ansatum" as known to all recent authors is the one originally described by Ralfs in his ' British Desmids/ and therefore Ralfs must be regarded as the authority for this species. The Desmid partly described and figured by Hassall under the name of "Euastrum circulars" is most probably a form of E. ansatum, as was pointed out by Lundell in 1871. Hassan's description, however, is so poor and his figure so had, that certain identification is impossible. The zygospores observed by Roy appear to have differed somewhat from those we have ourselves observed. Roy describes the zygospores as furnished with numerous " short, EUASTRUM. 29 stout, abruptly-sharp-pointed spines," whereas we find them covered with short, stout, blunt papilla?. The undulation at the sides of the semicells varies very much, so that we find it impossible to clearly define the " var. sublobatum" of Delponte. Yar. pyxidatum Delp. (PL XXXVI, figs. 14, 15.) E. ansatum var. pyxidatum Delp. Desm. subalp. 1873, p. 103, t. 6, f. 32-34; De Toni, Syll. Alg. 1889, p. 1097. Semicells almost three-lobed owino- to the O development of the undulation above the basal angles, upper portion of lateral margins deeply sinuate, "polar lobe " subquadrate with rounded angles. Length 65-86 p ; breadth 33-42 p. ; breadth of isthmus 12-14 ^t; thickness 22-27 /x. SCOTLAND. — " Common" (Roy $ Bissett). AYe find it very rare ! IEELAXD. — G-alwav ! b Geogr. Distribution. — Poland. Italy. 15. Euastrum obesum Josh. (PI. XXXVI, figs. 16, 17.) Euastrum obesum Josh. Burmese Desm. 1886, p. 638, t. 23, f. 19, 20; De Toni, Syll. Alg. 1889, p. 184 ; Xordst. Index Desm. 1896, p. 184 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 62. Helierella obesa Kuntze, Revis. gen. plant. 1891, p. 899. Cells of medium size, about twice as long as broad, deeply constricted, sinus narrowly linear; semicells pyramidate, with broadly-rounded basal angles, lower part of lateral margins convex, upper part slightly concave, apex widely subtruncate with rounded angles having a narrow median incision. Side view of semi- cell ovate-pyramidate, apex rounded. Vertical view broadly elliptical, lateral margins very slightly biundulate. Cell- wall smooth. Zygospore unknown. Length 50-111^; breadth 30-59 /i; breadth of apex 17-28 JJL; breadth of isthmus 9-21 p.. EXGLAXD. — Mossdale Moor, Widdale Fell, X. Yorks (large specimens) ! 30 BRITISH DESMIDIACE.E. Geofjr. Distribution. — India. Burmali. Singapore (var.). Sumatra. Madagascar (var.). All the examples of this species which we have seen possessed a smooth cell-wall. Turner also found that Indian specimens had a smooth cell-wall; his measurements are : — length 58-65 /m ; breadth 37-44 /n ; breadth of isthmus 1 6-17 /m. Joshua describes the cell-wall as of " a faint flesh-colour, sometimes indistinctly granulated." His original measure- ments are : — length 50-80 in ; breadth 30-35 /.t ; breadth of isthmus 9-15 /u. It is distinguished from E. ansatum by its relatively-greater breadth and by the broadly-rounded basal part of the semi- cells. There is also an absence of the longitudinal lines of punctulations which are such a characteristic feature of E. ansatum. 16. Euastrum pingue Elfv. (PI. XXXVII, fig. 1.) Euastrum sp. Arch, iu Quart. Journ. Micr. Sci. 1871, p. 93 (according to Roy). Euastrum pingue Elfv. Anteck. Finska Desm. 1881, p. 7, t. 1, f . 3 ; Wolle, Desm. U.S. 1884, p. 105, t. 27, f. 1-3 ; De Toni, Syll. Alg. 1889, p. 1098 ; Roy & Biss. Scott. Desm. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 201. E. Armstrongianum Arch, in Ann. Mag. Nat. Hist. 1883, p. 213. Helierella pinguis Kuntze, Eevis. gen. plant. 1891, p. 899. Cells small, almost H times longer than broad, very deeply constricted, sinus slightly open for more than half its length, then narrowed; semicells rounded- pyramidate, basal angles broadly rounded (faintly subrectangular) upper portions of lateral margins retuse ; apex convexo-truncate, with a widely-open, shallow, median notch. Cell- wall scrobiculate ; scrobi- culations larger in the centre of the semicells, at the apex, and at the basal angles, causing these parts of the cell-wall to appear rough on the surface ; with a larger, somewhat irregular scrobiculation in an excentric position near the centre of the semicells. Semicells with a small papilla at each basal angle at the beginning of the sinus ; also with a large granule in the middle and close to the isthmus. Side view of semicell ovate, apex rounded, sides slightly retuse just below the apex ; with a granule at each side at the base, close to EUASTKUM. 31 the isthmus. Vertical view elliptic, with rounded poles, slightly inflated in the middle on each side. Zygospore unknown. Length 56-60 ^ ; breadth 40-41 ju, ; breadth of apex 19-21 |u ; breadth of isthm. 9'6-12 /* ; thickness 26-28 p. SCOTLAND. — Xear Cambus-o'-May, Aberdeen : G-len e.' j Cloya, Forfar ; Glen Coe, Argyll (Roy $m Biss^ft). Ehiconich, Sutherland ! IEELAND. — Connemara, G-alway (ArcJter). Geocjr. Distribution. — Finland. United States. 17. Euastrum insigne Hass. (PI. XXXVII, figs. 2-5.) Euastrum insigne Hass. Brit. Freshw. Alg. 1845, p. 21, t. 91, f. 2 ; Ealfs, Brit. Desm. 1848, p. 83, t, 13, f. 6 ; Arch, in Pritch. Infus. 1861, p. 729, t. 3, f . 12 ; Babenk. Flor. Em-op. Algar. Ill, 1868, p. 184 ; Kirolm. Alg. Schles. 1878, p. 158 ; Cooke, Brit, Desru. 1886, p. 69, t. 33, f. 4 ; Hansg. Prodr. Algenfl. Bohin. 1888, p. 206 ; De Toni, Syll. Alg. 1889, p. 1092 ; West, Alg. N. Wales, 1890, p. 287 ; Alg. W. Ireland, 1892, p. 137 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Eoy & Biss. Scott. Desui. 1893, p. 177 ; West £ G. S. West, Some N. Amer. Desm. 1896, p. 242 ; Nordst. Index Desm. 1896, p. 147 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 62 ; Alg. N. Ireland, 1902, p. 28. Didymidium (Euastrum) insigne Eeinsch, Algenfl. Franken, 1867, p. 130. Euastrnm mammillosum Wolle in Bull. Torr. Bot. Club. 1883, p. 18, t. 27, f . 21 ; Desm. U. S. 1884, p. 102, t. 26. f. 14, 15 (figures bad) ; De Toni, Syll Alg. 1889, p. 1078. E. insigne b. typicum Eacib. Nonn. Desm. Polon. 1885, p. 92. E. insigne c. montanum Eacib. 1. c. t. 13, f. 1. Helierella insignis Kuntze, Eevis. gen. plant. 1891, p. 898. H. mammillosa Kuntze, 1. c. p. 899. Euastrum insigne var. elegans Schmidle Beitr. Alg. Schwarzwald. 1893, p. 105, t. 6, f. 7, 8. E. insigne var. mammillosum (Wolle) Turn. Freshw. Alg. E. India, 1893, p. 79. Cells of medium size, about twice as lono' as broad, . deeply constricted, sinus widely open, narrowed towards the extremity ; semicells widely deltoid in the basal portion, then narrowed into a neck, which widens again into an obyersely-deltoid apex, basal and apical angles rounded, frequently with an undulation on the margin just aboye the basal angle, apex truncate with a narrow median incision ; semicells with a large, sub- mamillate, downwardly-directed protuberance within 32 BRITISH DESMIDIACE^E. each basal angle, which projects over the edge of the sinus. Side view of semicell elongate-pyramidate, angles at base submamillate, lower part of sides convex, upper part of sides concave ; with a dilated apex, the angles of which are bluntly mamillate and upwardly directed. Vertical view oblong-rectangular, with a conical-mamillate protuberance in the middle of each truncate pole, lateral margins retuse in the centre; polar lobe in the form of an oblique cross, the four processes of which are mamilliform. Cell-wall scrobi- culate, scrobiculations larger at all the angles, the surfaces of which become rough (sometimes almost papillate). Zygospore unknown. Length 108-135 ft; breadth 57-70 p ; breadth of apex 29-37 /u ; breadth of isthmus 13-15'5ju; thick- ness 32-36 fi. ENGLAND. — Cumberland ! Westmoreland ! (Ralfi). Lancashire ! TT. and X. Yorks ! Surrey ! Hants. (Rolfs). Devon ! (Bennett). WALES. — Common in Carnarvonshire (up to 2,200 ft. on Glyder Fach) and Merioneth ! SCOTLAND. — Sutherland !, Ross, Inverness !, Banff, Aberdeen !, Kincardine, Forfar !, Perth !, Argyll, Arran (Roy $' Bissett). Harris and Lewis, Outer Hebrides ! IRELAND. — Glen Caragh, Cromagloun, and Tore Mt., Kerry ! Pool near Louo'li Glentornan, Donegal ! v O O Dublin and Wicklow (Archer). Geogr. Distribution. — France. Germany. Austria and Galicia. Hungary. Norway. Sweden. Finland. Poland. Faeroes. United States. This species is often abundant in mountain bogs and the boggy margins of mountain tarns, in which situations it is commonly found amongst the leaves of a submerged form of Sphagnum cuspidatum. It exhibits considerable variation in the leno'th of the "neck " and in the form of the basal ano'les O O of the semicells. These variations are connected by every intermediate state, so that it is impossible to clearly define such forms as " var. montanum E/acib." or "var. elegans Schmidle." The Desmid described and figured by Wolle EUASTRUM. 33 from the United States as " Euastrum mammilloaum" is a bad illustration of a form of E. insigne. The plant that Wolle figures as E. insigne is now known as E. orientale Turn. Wolle never appeared to clearly understand the nature of Euastrum insigne Hass. 18. Euastrum intermedium Cleve. (PL XXXVII, fig. 6.) Euastrum intermedium Cleve, Sverig. Desm. 1864, p. 484. t. 4, f . 1 ; Lund. Desm. Suec. 1871, p. 21, t. 2, f . 4 ; De Toni, Syll. Alg. 1889, p. 1093 ; Eichler, Mat. flor. Miedz. 1893, p. 61 ; 1894, p. 130; Eoy & Biss. Scott, Desm. 1893, p. 177 ; West & O. S. West, Some N. Amer. Desm. 1896, p. 242, t. 14, f . 18, 19 (forma) ; Nordst. Index Desm. 1896, p. 148. E. insigne b. intermedium Eabenh. Flor. Europ. Algar. Ill, 1868, p. 184. Holocystis intermedia Benn. Freshw. Alg. Eng. Lake Distr. 1886, p. 8. Helierella intermedia Kuntze, Revis. gen. plant. 1891, p. 898. Cells small, almost If times as long as broad, deeply constricted, sinus widely open but narrowed at the extremity; semicells three-lobed, with a large open sinus between the polar and lateral lobes ; lateral lobes obtusely conical ; polar lobe somewhat anvil-shaped, angles acutely rounded, apex convexotruncate with a narrow median incision ; semicells with two pro- tuberances across the middle of the basal half (between the two lateral lobes), and with two very small pro- tuberances on the polar lobe, one on each side of the median incision. Side view of semicell elongate- pyramidate, with a protuberance on each side near the base, lateral margins concave, and with a slight swell- ing on each side of the apex, which is rounded (or rounded-truncate). Vertical view elliptical, poles acutely rounded, with two prominent protuberances on each side near the middle; polar lobe elliptical, with two slight swellings on each side near the middle. Cell- wall smooth. Zygospore unknown. Length 54-68 /x ; breadth 31-40 p. ; breadth of apex 20-26 p.; breadth of isthmus 9-10 /x; thickness 20-25 p.. ENGLAND. — Cumberland (Bennett) . 3 34 BEITISH DESMIDIACEJS. SCOTLAND. — Locli Inver, Sutherland!; Poolewe, Ross; South Birsemore, Aberdeen ; Grlen Clova, Forfar ; Arnbathie Loch, Perth ; Glen Coe, Argyll (Roy & Bissetf). Rhiconieh, Sutherland ! Geogr. Distribution. — Norway. Sweden. Poland. Greenland. Ceylon (var.). Azores. United States. 19. Euastrum Webbianum Turn. (PI. XXXVII, fig. 7.) Euastrum Welbianum Turn. Freshw. Alg. E. India, 1893, p. 86 (formee major et minor}, t. 22, f . 4 ; Turn. Desmid Notes, 1893, p. 343, f . 4 (forma major). Cells rather small, about twice as long as broad, deeply constricted, sinus widely open but narrowed towards the extremity ; semicells subpyramidate, with concave sides, and projecting, subconical (slightly up- turned) basal angles, apex truncate with a narrow median incision. Cell- wall smooth. Forma minor: length 26-30^; breadth 13- 16 ft; breadth of isthmus 4 p. Forma major : length 58 //, ; breadth 28 //, ; breadth of isthmus 8 //,. ENGLAND. — Sutton Park, Warwick (forma major, Turner). Geogr. Distribution. — X. India (forma minor). This small "Euastrum," which has been but imperfectly described by Turner, appears to us as very probably two dislocated cells (each in an oblique position) from a filament of Desmidium Swartzii or some allied species. 20. Euastrum Sendtnerianum Reinsch. (PL XXXVII, fig. 8.) Euastrum Sendtnerianum Eeinsch, Spec. Gen. Alg. 1867, p. 119, t. 21, f. C. II 1-6 ; De Toni, Syll. Algar. 1889, p. 1079. Didymidium (Euastrum) Sendtnerianum Eeinsch, Algenfl. Frank. 1867, p. 135, t. 9, f . 4. Cosmarium (Euastrum} Sendtnerianum Wolle in Bull. Torr. Bot. Club. 1885, p. 3, t. 47, f. 30-31 ; Wolle, Freshw. Alg. U.S. 1887, p. 29, t, 57, f. 30, 31 ; Gutw. Flor. Glon. Okolic Lwowa, 1891, p. 40. Helierella Sendtneriana Kuntze, Revis. gen. plant. 1891, p. 899. EUASTKUM. 35 Cells very small, about twice as long as broad, oblong-elliptic in outline, deeply constricted, sinus narrowly linear and dilated at the extremity ; semi- cells semi-elliptic, with four undulations up each side and an emarginate apex. Side view of semicell ovate- elliptic ; vertical view elliptic. Cell-wall smooth. Zygospore unknown. Length 23-27 p.; breadth 12-15 /* ; breadth of isthmus 4 ^ ; thickness 6-8 JJL. Geo'/r. Distribution. — Germany. Galicia in Austria. The typical form of this species is unknown in the British Islands. Ghitwinski gives as the measurements of his Austrian specimens : length 29 ^ ; breadth 17 fj. ; breadth of isthm. 7 /m. The figure we give is exceedingly poor, but as it is an exact copy of Reinsch's original, this could only be expected. Var. latius Roy & Biss. E. Sendtnerianum var. latius Eoy & Biss. Scott. Desm. 1893, p. 177; Nordst. Index Desm. 1896, p. 232. Larger than the type, with broader apices. Length 43*2 ^ ; breadth at base of semicells 25'6 //,, at apex 19*2 p.. SCOTLAND. — Near Den of Maidencraig, Aberdeen (Eon £ Bissett). We are unacquainted with this variety and are unable to give a figure of it. 21. Euastrum rostratum Ealfs. (PI. XXXVII, figs. 11-13.) Euastrum rostratum Ealfs ill Ann. Mag. Xat. Hist. 1844, p. 192, t. 7, f. 5; Hass. Brit. Freshw. Alg. 1845, p. 382, t. 91, f . 8 ; Ralfs, Brit. Desm. 1848, p. 88, t. 14, f. 6 ; Arch, in Pritch. Infus. 1861, p. 730, t. 1, f. 26 ; Cooke, Brit. Desni. 1886, p. 73, t. 35, f. 2 (figures partly copied from Ealfs, and bad) ; De Toni, Syll. Alg. 1889, p. 1099 ; ? West, Freshw. Alg. W. Ireland, p. 138; Eoy & "Biss. Scott. Desm. 1893, p. 177; West & G. S. West, Alg. S. England, 1897, p. 483; Alga-fl. Yorks, 1900, p. 62. E. elegans b. rostratum Rabenh. Flor. Europ. Algar. Ill, 1868, p. 186. Helierella rostrata Kuntze, Eevis. gen. plant. 1891, p. 899. Cells small, a little more than 1-| times longer than broad, very deeply constricted ; sinus narrowly linear, 36 BRITISH DESMIDIACEJL dilated at the extremity and slightly open outwards ; semicells subpyramidate in outline, more or less three- lobed ; polar lobe quadrate-cuneate, apex convex with a deep and open median notch, a short, blunt spine at each outer angle, and a thickening at each angle of the apical notch ; lateral lobes bilobulate, upper lobule rounded and submamilliform, or sub- quadrate and emarginate, upwardly directed, lower lobule emarginate or bluntly tridentate, horizontally disposed ; semicells with a large protuberance in the centre above the isthmus, a large rounded wart on each side of the apical incision and near the base of the polar lobe, a small wart within each lower lateral lobule, and one or two small granules within both upper and lower lateral lobules. Side view of semi- cell ovate-pyramidate, apex rounded, with a prominent protuberance on each side near the base, and a wart on each lateral margin half-way between the basal O il protuberance and the apex. Vertical view elliptic, with angular poles and a large protuberance in the middle on each side. Cell-wall smooth. Zygospore globose, furnished with simple, blunt spines. Length 39-49 /a ; breadth 25-35*5 /< ; breadth of isthmus 6*5-8 fj. ; thickness 20-24 /u. ENGLAND.- -Westmoreland ! (Rolfs}. JN". and E. Yorks I Lancashire ! Warwick (Wills). Sussex (Rolfs). Hants (Bennett). Devon! Cornwall ! (Ralfs). WALES. — Capel Curig, Carnarvonshire (Roy). Dol- gelly, Merioneth (Ralfs). SCOTLAND. — General but scarce ! (Roy fy Bissett). IRELAND. — Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Geogr. Distribution. — France. Germany. Galicia in Austria. Norwav. Sweden. Denmark. Bornholm. . Finland. Poland. N. Russia. Faeroes. Spitsbergen. Greenland. India. Ceylon. Burmah (var.). Aus- tralia (var.). New Zealand (var.). Madagascar (var.). United States. EUASTfilLM. 37 This is a somewhat rare British species with very distinctive characters, one of the most prominent being the large smooth protuberance in the centre near the base of each semicell. The large warts on either side of the apical incision, and near the base of the polar lobe, are also very characteristic, but were overlooked by Ralfs. In fact, the description of this Desmid given by Ealfs is very incomplete, and has caused many observers to go astray with regard to the exact identity of E. rostratum. The Euastra figured by Wolle, 'Desm. U. S/ t. 27, figs. 8 and 9, as " E. rostratum " do not belong to this species. Note. — E. rostratum var. cumbricum Benn. Freshw. Alg. Eng. Lake Distr. II, 1888, p. 5, t. 1, f. 13. It is impossible to say with certainty that Bennett's variety belongs to E. roxtratum. His figure is too crude and the apex of the semicell is most extraordinary. It would appear to differ principally in the uniformity of the tabulation and the widely excavated apex. Length 45-50 /LI ; breadth 25 /u. 22. Euastrum Turnerii West. (PL XXXVII, figs. 9, 10.) "Euastrum sp. ad. E. denticulatum accedens " Xordst. Freshw. Alg. N. Zeal. 1888, p. 35, t. 3, f. 11 [£. denticulatum Mask., 1889, uon Gay]. Euastrv.m Turnerii West Alg. W. Ireland, 1892, p. 141, t. 20, f. 18 Nordst. Index Desui. 1896, p. 264 ; West & G. S. West, Alg. N. Ireland 1902, p. 29. Cells small, about 1^ times longer than broad, deeply constricted, sinus narrowly linear with a dilated ex- tremity; semicells pyramidate, more or less three- lolled ; polar lobe short and very broad, oblong-rect- angular, lateral margins retuse, apical angles furnished with a short divergent spine, apex truncate, with four undulations and a narrow median incision ; lateral lobes bilobulate, both upper and lower lobules truncato- emarginate ; semicells with a small tumour in the centre ornamented with a rine; of granules. Cell-wall o o furnished with a number of granules within the polar and lateral lobes. Side view of semicell ovate pyrami- date, apex acute, with a truncate granulate protuber- ance near the base on each side. Vertical view elliptic, 38 BEITISH DESUIDIACE./E. poles acutely rounded, with a truncate granulate pro- tuberance at the middle on each side. Zygospore unknown. Length 39-50 /x ; breadth 28-33 /x ; breadth across polar lobe 20-23 p. ; breadth of isthmus 7-9 /x ; thick- ness 18-20 /x. ENGLAND. — Hampsfell, Lancashire ! SCOTLAND. — Rhiconich, Sutherland ! Aboyne, Aber- deen ! IRELAND. — Near Grlenties and Lough Nacally, Donegal ! Derryclare Lough, Galway ! Geogr. Distribution . — Australia. This species differs from E. denticulatum (Kirclin.) Gay in its larger size, in the form of the polar lobe, and in the bilobulate condition of the lateral lobes. 23. Euastrum spinosum Ralfs. (PI. XXXVII, figs. 14, 15.) Euastrum spinosum Ralfs in Ann. Mas^. Nat. Hist. 1844, xiv, p. 192, t. 7, f . 6 ; Hass. Brit. Freshw. Alg. 1845, p. 384, t. 91, f . 9. E. elegans (Breb.) Kiitz. v&r.spinosv.m Ealfs, Brit. Desm. 1848, p. 89, t. 14, f . 7 f-l ; Kabenh. Flor. Europ. Algar. Ill, 1868, p. 185 ; Kirchn. Alg. Schles. 1878, p. 159 ; Cooke, Brit. Desm. 1886, p. 74, t. 35, f. 5 ; Hansg. Prodr. Alcjenfl. Bohui. 1888, p. 252 ; West & G. S. West, Some N. Amer. Desm. 1896, p. 244, t, 14, f. 27. Cells small, almost If times longer than broad, deeply constricted, sinus narrowly linear ; semicells pyramidate, with convex sides which are gently sinuate, bearing one or two dentic illations on the basal sinua- tion, and a short, upwardly-directed spine on each of the other two sinuations, apex rounded-truncate, with a rather deep and narrow median incision ; semicells with a quadriverrucose protuberance in the middle above the isthmus, a wart-like granule on each side of the apical incision, and a number of small granules or fine denticulations within the marginal sinuations and at the apex. Side view of semicell ovate-pyramidate, apex rounded, with a small emarginate protuberance at the base on each side, lateral margins undulate. EUASTRUM. 39 Vertical view elliptic, with pointed and denticulate poles, lateral margins granulate or denticulate, and with a broad emarginate protuberance at the middle on each side. Zygospore globose, furnished with numerous, rather bluntly-pointed spines. Length 28-38'5/x; breadth 18-23 p.; breadth of isthmus 5'5-6*5ft; thickness 12'5-13*5 p. ; diam. zygosp. without spines 26-30 /x ; length of spines 7'5-9'6 p.. ENGLAND. — Cornwall (Ra Ifo) . Dolgelly (Ralfs). IRELAND. — Dublin and Wicklow (Archer). Geogr. Distribution. — Germany. Sweden. India. United States. Guiana. We think E. spinosum Ralfs possesses sufficiently distinctive characters to allow of its remaining as a distinct species. The gently-sinuate margins of the semicells, the absence of any trace of a " neck/7 and the spines on the lateral margins, dis- tinguish it from ordinary forms of E. elegans. Ralfs also states that the zygospore possesses more slender and more numerous spines than that of E. elegans. The Euastra figured by Wolle, ' Desm. U. S.' t. 27, figs. 4-7, as {t E. spinosum" do not belong to this species. 24. Euastrum bidentatum Nag. (PI. XXXVII, figs. 16-19.) Euastrum bidentatum Nag. Gatt. einzell. Alg. 1849, p. 122, t. 7 D, f. 1 a-f; West & G. S. West, Alsra-fl. Yorks. 1900, p. 62 ; Alg. N. Ireland, 1902, p. 29. E. elegans (Breb.) Kiitz. var. bidentatum (Nag.) Jacobs. Desm. Danern. 1875, p. 191 ; Borg. Bornhohn. Desm.-fl. 1889, p. 143, t. 6, f . 2 ; Borge, Chlorophy. Norska Fimnark. 1892, p. 6 ; Eoy & Biss. Scott. Desin. 1893, p. 176 ; Borg. Ferskv. alg. Ostgronl. 1894, p. 31 ; West & G. S. West, Alg. S. England, 1897, p. 483. E. elegans (Breb.) Kiitz. var. speciosum Boldt, Desmid. Gronland, 1888, p. 9, t. 1, f. 10, 11 ; De Toni, Syll. Alg. 1889, p. 1102 ; Schmidle, Beitr. alp. Alg. 1895, p. 22. Cells small, about li- times longer than broad, deeply constricted, sinus narrowly linear with a dilated ex- tremity; semicells subpyramidate, with bilobulate 40 BRITISH DESMIDIACE.E. sides; lower lobule subrectangular, sometimes emar- ginate, and furnished with two or three sharp granules ; upper lobule rounded or rounded-truncate, rarely emarginate, sometimes furnished with one or with two sharp granules ; apex convex, sometimes slightly undulate, with a deep median notch, which may be somewhat open or closed, with a short, blunt spine at each apical angle, and usually with a thickening at the angles on each side of the apical incision; semicells with a granulated protuberance in the centre above the isthmus (number and disposition of granules vari- able), with a large granule below and on each side of the apical incision (sometimes absent), and with a few variously-disposed granules within the lateral lobules and the apex. Side view of semicell ovate, with a protuberance (usually emarginate) on each side near the base, and a granule on each side higher up on the lateral margins ; apex rounded and tridenticulate. Vertical view elliptic, with a protuberance (emarginate or trigranulate) at the middle on each side, poles furnished with acute granules or denticulations. Zygospore globose, furnished with numerous strong simple spines, most of which are curved. Length 51-61 ju; breadth 32-39 p ; breadth of apex 25-29 /x; breadth of isthmus 6*3-11 /LI ; thickness 21-23 /A; diam. of zygosp. without spines 40-42*5 /u,; length of spines 10-13 p,. ENGLAND. — Westmoreland ! N. and W. Yorks ! Lancashire ! Essex ! Oxfordshire ! Surrey ! Kent ! Hants, (zygospores from the New Forest) ! Devon ! Cornwall ! WALES. — General throughout Carnarvonshire (at 2,200 ft. on Glyder Fach) ! SCOTLAND. — Common ! (Roy $ Bissett). Outer Hebrides ! Orkneys ! Shetlands ! IRELAND. — General ! Geogr. Distribution. — Germany. Norway. Sweden. Denmark. Bornholm. Iceland. Greenland. Russia. United States. Brazil. EUASTRUM. 41 E. bidentatum Xag\ is a species well differentiated from E. elegans by its lobulate margins,, its larger and more de- pressed apices, and its ornamentation. It is also larger than most forms of E. elegans, although it is connected with that species by E. elegans var. NOV& Semliex and E. elegans var. ornatum. It is generally distributed all over the British Islands, and retains its distinctive characters in a very constant manner. Almost the only variation met with is in the form of the lateral «/ lobules and in the disposition of the surface ornamentation. The central protuberance varies much in the number and arrangement of its granules. The figures given by Xageli are fairly good in outline, but he does not indicate the markings which are always present on this species. Most probably the figure of E. elegans in RalfV 'Brit. Desm./ t. 14, f. 7a, is a form of this species. 25. Euastrum pictum Borg. (PI. XXXVIII, fig. 1.) Euastrum pictum Borg. Desm. Brasil. 1890, p. 34, t. 3, f. 19. Cells relatively small, a little more than 1-J- times longer than broad, deeply constricted, sinus narrowly linear with a dilated extremity ; semicells subquadrate, three-lobed ; polar lobe short and much dilated, apex convex and undulate, with an open median incision, apical angles furnished with a short, strong spine; lateral lobes bilobulate, upper lobule small and fur- nished with two small teeth, lower lobule larger and furnished with three small teeth ; semicells in centre with a large granulate protuberance, and with smaller granulate protuberances within each lateral lobule and each half of the polar lobe. Vertical view elliptic, poles denticulate, and with a median granulated pro- tuberance on each side. Z y gospore unknown . Length 72 /n ; breadth 43 /t ; breadth of isthmus, 11 /i; thickness, 27 /n. . Distribution. — Brazil. United States (var). Absolutely typical forms of E. pictum do not occur in the British Isles. Those already recorded (consult West, 'Alg. 42 BRITISH DESMIDIACE2E. W. Ireland/ 1892, p. 139), and others that we have seen, bear a striking resemblance to large forms of E. bidentatum Nag. They differ from E. pic-turn in having the lateral teeth reduced to acute granules, and in the replacement of the special, granulated -protuberances by single large granules. They would be almost equally well placed under E. bidentatum, except for their size and additional protuberances. Length 79 /n ; breadth 52 // ; breadth of isthmus 14 /m. (PL 38, fig. 2.) WALES. — Moel Siabod and Llyn Ogwen, Carnarvonshire ! SCOTLAND. — Rhiconich, Sutherland ! IRELAND. — Lakes near Recess, Oorid and Arderry Loughs, Gal way ! Glen Caragh, Lough Guitane, Castletown and CarrantuohilL Kerrv ! 7 *. 26. Euastrum divaricatum Lund. (PI. XXXVIII, figs. 3, 4.) Euastrum divaricatum Lund. Desm. Sviec. 1871, p. 21, t. 2, f . 5 ; ? Wolle, Desin. U. S. 1884, p. 104, t. 26, f . 18-19 ; De Toni, Syll. Alg. 1899, p. 1100 ; Turner, Freshw. Mg. E. India, 1893, p. 84, t. 11, f. 22 ; Eichler, Mat. flor. Meidz. 1894, p. 130. Helierella divaricata, Kuntze, Revis. gen. plant. 1891, p. 898. Cells small, 1 J times longer than broad, very deeply constricted, sinus narrowly linear with a dilated extremity ; semicells subtriangular, rapidly attenuated to the convexo-truncate apex, more or less three-lobed ; polar lobe very broad, rectangular-oblong, each apical angle furnished with a small spine, median incision deep and open ; lateral lobes bilobulate, upper lobules widely triangular and rounded, lower lobules truncate- t/ O rounded, furnished with a denticulation at the entrance to the sinus and with a horizontal or upwardly- diverging spine ; semicells with a protuberance in the middle above the isthmus, biverrucose, triverrucose, or granulate, with a large rounded granule on each side of the apical incision at the base of the polar lobe, and with about four granules within the lateral margins o o and two within the apex. Side view of semicell ovate, apex furnished with a small spine, and with a granulate or emarginate protuberance at each side near the base. EUASTKHM. Vertical view elliptic, with a spine at each pole, and a granulate or emarginate protuberance at the middle on each side. Zygospore unknown. Length 3(3-45 p.; breadth 31-36 //,; breadth of isthmus 6-7 p; thickness 16-19 /x. SCOTLAND. — G-len Coe, Argyll (Roy and Bissett). Loch O «/ \ e / Iron Sineur, Perth! (J. Murray). Rhiconich, Suther- land ! Geogr. Distribution. — Austria and G-alicia. Norway. Sweden. Denmark. Poland. N. Russia. India (var.). United States. West Indies and Brazil (var.). This is a very rare species in the British Islands and has essentially a western distribution. 27. Euastrum dubium Nag. (PI. XXXVIII, figs. 5-8.) Euastrum binale Ralfs, Brit. Desm. 1848, t. 14, f . 7 d. E. dubium Nag. Gatt. eing. Alg. 1849, p. 122, t. 7 D, f. 2 ; Nordst. Index Desm. 1896, p. 113. E. lobulatum Breb. Liste Desm. 1856, p. 124, t. 1, f . 4 ; West & G. S. West Alg. Notes II, 1900, p. 290 ; Alga-fl. Yorks. 1900, p. 63 ; Alg. N. Ireland, 1902, p. 29. E. elegans (Breb.) Kiitz. var. lobulatum (Breb.) Jacobs. Desm. Danein. 1875, p. 191. E. binale (Tiirp.) Elirenb. var. rotundata Istvanffi, Diag. prsev. Alg. nov. Hungar. 1887, p. 236 (according to Istvanffi). E. erosum Lund. var. notabile West, Alg. Eng. Lake Distr. 1892, p. 723, t. 9, f. 17 ; West & G. S. West, Alg. S. England, 1897, p. 484. Cells very small, 1^- times longer than broad, very deeply constricted, sinus narrowly linear witli a slightly- dilated extremity ; semicells truncato-pyramidate, five- lolled ; polar lobe short, oblong-rectangular, apex trun- cate with a narrow median incision, apical angles furnished with a small conical granule ; upper lateral lobes rounded ; lower lateral lobes very slightly larger than the upper ones, rounded, obliquely truncate, or sometimes slightly emarginate ; semicells with two granules within the apex, one on each side of the notch, with two faint granules within each basal angle, often with a faint granule below the apical notch, and with a slight trace of a smooth central protuberance. 44 BRITISH DESMIDIACE^E. Side view of semicell ovate-oblong, apex acutely rounded, very slightly dilated on each side at the base. Vertical view elliptic-oblong, poles acute, and with a very slight swelling (sometimes absent) at the middle on each side. Zygospore unknown. Length 26* 5-3 3 ft; breadth 19-21/>t; breadth of isthmus 4-6 p.; thickness 10-12'5/x,. ENGLAND. — Westmoreland! ~N.9 W., and E. Yorks ! Lancashire ! Lincolnshire ! Essex ! Wilts ! Surrey ! Devon ! Cornwall ! WALES. — Bogs above Capel Curig, Glyder Fach at 2,200 ft,, near Llyn Idwal, Y Foel Fras, and Rhyddu, Carnarvonshire ! SCOTLAND. — General! (Roy fy Bissett). Up to 3,500 ft. on Loclmagar, Aberdeenshire ! Common in the Outer Hebrides ! Orkneys ! Shetlands ! IRELAND. — Donegal ! Mayo ! Gal way ! Kerry ! Dublin and Wicklow (Archer). Down! Geogr. Distribution. — France. Norway. Sweden. Denmark. Italy. We gave full reasons for considering Euastrum erosum var. notaljile as identical with E. lob/datum Breb. in the ' Journal of Botany/ 1900, p. 290, and in the 'Alga-flora of Yorkshire/ p. 63. We also think that E. lobulatum is correctly identified with Nageli's E. dubium, which was described seven years previously. Nageli's figures are not good, but there can be no question that they represent the same plant as that described and figured by Brebisson under the name of E. lobulatum. It is a widely distributed species and is found in the boggy districts of every part of the British Islands. It is easily distinguished from E. binale by its relatively greater length, its equal tabulation at the sides, and by the markings oil the semicells. Var. anglicamim (Turn.) nob. (PI. XXXVIII, fig. 9.) Euastrum anglicanum Turn. Desm. Notes, 1893, p. 343, fig. 6. Apex of semicells convexo-truncate, apical incision open; with a few scattered granules within the lateral EUASTRUJil . 45 lobes, and with five granules arranged on a central protuberance. Length 36 /x; breadth 22 /*; breadth of isthmus 6 /x. ENGLAND. — Trelleck Common, Monmouth (Turner). Var. cambrense (Turn.) nob. (PL XXXVIII, fig. 10.) Euastrum cambrense Turn. Desm. Notes, 1893, p. 343, f. 1. Upper lateral lobes furnished with a short, upwardly- directed spine ; with six granules forming a ring on the central protuberance. Length 32 /x ; breadth 20 p ; breadth of isthmus 5 /x ; thickness 9*5 p.. WALES. — Near Dolbadarn Castle, Carnarvonshire (Turner). Var. Snowdoniense (Turn.) nob. (PL XXXVIII, %. no Euastrum Snowdoniense Turn. Desm. Notes, 1893, p. 343, f. 2. Cell-wall of lateral lobes and polar lobe thickened at the margin ; apical notch open ; with three small pro- tuberances (?) forming a triangle in the centre of the semicell. Length 31 /A; breadth 20 /x; breadth of isthmus 6*5 p.. WALES. — Snowdon, Carnarvonshire (Turner). 28. Euastrum erosum Lund. (PL XXXVIII, figs. 12, 13.) Euastrum erosum Lund. Desni. Suec. 1871, p. 22, t. 2, f . 6 ; Cohn, Desm. Bongo. 1879, t. 11, f. 12 ; Cooke, Brit. Desm. 1886, p. 77, t, 35, f. 12 ; De Toni, Syll. Alg. 1889, p. 1072; West, Alg. aq. dulc. Lusitan. 1892, p. 1501 ; Eoy & Biss. Scott. Desni. 1893, p. 176 ; Nordst. Index Desm. 1896, p. 119 ; West & Gr. S. West, Alga-fl. Yorks. 1900, p. 63. Helierella erosa Kuntze, Revis. gen. plant. 1891, p. 898. Cells very small, 1|— If times longer than broad, deeply constricted, sinus narrowly linear ; semicells somewhat hexagonal, the base broader than the re- maining sides, angles rounded, lower portions of lateral margins parallel and retuse, upper portions converging 46 BRITISH DESMIDIACE.E. towards the apex, and retuse, apex truncate and retuso-emarginate. Side view of semicell quadrate- rectangular, with attenuated poles which are o-crenu- late. Vertical view subrectangular, with slightly convex sides, poles broadly truncate and 3-crenulate. Cell-wall smooth. Zygospore unknown. Length 32-39 //,; breadth 20-23 p.; breadth of isth- mus 7'5-8'5/x; thickness 11-16 p. ENGLAND.- -Westmoreland (Bissett). Mickle Fell, N. Yorks ! Hants, Devon, and Cornwall (Bennett). WALES. — Capel Curig and Pen-y-gwrydd, Carnarvon- shire (Roy). SCOTLAND. — Ross, Inverness !, Aberdeen, Kincardine, Forfar, Perth, Argyll and Arran (Roy fy Bissett). IRELAND.- -Dublin and Wicklow (Archer). Georjr. Distribution. — Germany. Portugal. Norway. Sweden. India (form). Central Africa. United States. E. erosum differs from E. dubium in. the character from which the species derives its name, viz., the crenulated poles of the side and vertical views. It is also less lobecl, with a less deep apical incision, and is completely destitute of any granulation on the surface. O 29. Euastrum pulchellum Breb. (PI. XXXVIII, figs. 14, 15.) Euastrum pulchellum Breb. Liste Desm., 1856, p. 124, t. 1, f . 5 ; Arch, in Pritcli. Infiis., 1861, p. 730; Eabenh. Flor. Europ. Algar. Ill, 1868, p. 186; De Toni, Syll. Alg. 1889, p. 1106; Roy. & Biss. Scott. Desin. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 211 ; West & G. S. West, Alga-fl. Yorks, 1900, p. 63 ; Alg. N. Ireland, 1902, p. 29. Helierella pulchella Kuntze, Revis. gen. plant. 1891, p. 899. Cells small, about 1^ times longer than, broad, very deeply constricted, sinus narrowly linear with a slightly- dilated extremity ; semicells more or less three-lobed, with a shallow sinus between the lobes; polar lobe widely rectangular-oblong, apex truncate with a deep and narrow median incision, apical angles furnished with a short diverging spine; lateral lobes rounded EUASTKUM. 47 quadrate, ornamented with 6-8 acute granules (3-4 marginal) ; semicells with a triverrucose protuberance in the centre above the isthmus, a large rounded granule on each side of the apical incision, and often a small granule at each angle of the apical incision. Side view of semicell ovate-oblong, with an emarginate protuberance at each side near the base, and a rounded granule at each side near the apex, apex rounded and furnished with a spine. Vertical view oblong, with rounded denticulate poles, and an emarginate protu- berance in the middle on each side. Zyo-ospore unknown. Length 37-40 M; breadth 28-33 ,u; breadth of isthmus 7-8 f.i ; thickness 19-20 n. EXGLAXP. — Bowness, Westmoreland ! Riccall Com- mon, E. Yorks ! Xew Forest, Hants ! Tremethick ]\loor, 'Cornwall ! SCOTLAND. — Sutherland !, Eoss, Aberdeen, Kincar- dine, Forfar, Perth, Argyll (Roy $• Bisxeit). Harris and Lewis, Outer Hebrides ! IRELAND. — Duno-loe, Loughs G-artan and Machugh, o Sproule's Lough, Donegal ! Lough Derryclare and Oughterard, Gralway ! . distribution. — France. Brebisson/s figure of E. pulcliellum is a very poor one and is inaccurate in its details. We find the species scarce but widely distributed in the British Islands. Perhaps the figure given by Wolle, f Desm. U. S.; t. 27, f. 9, of E. rostraium belongs to this species. Var. retusum nov. var. (PI. LXIV, fig. 17.) Lateral lobes less protuberant, broader, and slightly retuse on their outer margin, with the upper angles emarginate ; polar lobe with a convex apex and with the median notch widely open. Length 40 p,; breadth 26 ^', breadth of isthmus f— f ro p.. EXGLAXD. — Bowness, Westmoreland ! 48 BRITISH DESMIDIACE^. 30. Euastrum elegans (Breb.) Kiitz. (PL XXXVIII, figs. 16-21.) Heterocarpella elegans Breb. in Coeval, microscop. et usage, Paris, 1839, p. 72 (name only). Cosmarium elegans Breb. in Menegh. Synops. Desm. 1840, p. 222. Euastrum elegans (Breb.) Kiitz. Phycol. germ. 1845, p. 135 ; Ealfs, Brit. Desm. 1848, p. 89, t. 14, f . 7 6, c, and d •, Arch, in Pritch. Infus. 1861, p. 730; Rabenh. Flor. Europ. Algar III, 1868, p. 185; Cooke Brit, Desm. 1886, p. 74, t. 35, f . 3 ; De Toni, Syll. Alg. 1889, p. 1101 ; West, Alg. W. Ireland, 1892, p. 139 ; Roy. & Biss. Scott. Desm. 1893, p. 176 ; Nordst. Index Desm. 1896, p. 116 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 63 ; Alg. N. Ireland, 1902, p. 28 ; Scott. Freshw. Plankton, I, 1903, p. 525. E. elegans from declivis Reinsch, Spec. Gen. Alg. 1867, p. 124, t. 20, f. D III 1-3. Didymidium (Euastrum) elegans Reinsch, Algenfl. Frank. 1867, p. 136. Euastrum elegans a. typicum Kirchn. Alg. Schles. 1878, p. 159. E. declive Roy in Bates' Flora Leicestershire, 1886, p. 35. E. elegans var. Lundellii Istvanffi. Diag. praev. Alg. nov. Hungar. 1887, p. 236 (Ralfs I.e. fig. 7 5 and c). Helierella elegans Ktintze, Revis. gen. plant. 1891, p. 898. Cells very small, about 1^ times longer than broad, deeply constricted, sinus narrowly linear; semicells ovate-pyramidate, basal angles subrectangular, retuse- emarginate, above with the sides concave, superior angles apiculate, apex strongly convex (or broadly rounded) with a deep and narrow median incision; semicells with a triverrucose or a granulate protu- berance in the centre above the isthmus, the rest of the cell-wall generally smooth. Side view of semicell ovate, with a truncately-rounded apex, and an emar- ginate protuberance on each side above the base. Vertical view elliptic, with acute poles, and an emar- ginate protuberance in the middle on each side. Zygospore globose, furnished with simple acute spines. Length 29-36'5 p. ; breadth 19-22 p,; breadth of isthmus 5 '8-7 ^ ; thickness 10-14*5 ^ ; diam. of zygosp. without spines 20-29 /i; length of spines 7'5-9'5 /x. ENGLAND. — Cumberland ! Westmoreland ! (Ralfs). W., N., and E. Yorks! Lancashire! Cheshire (Ralfs}. Leicestershire (Roy). Essex ! Warwick (Wills). Gloucestershire (Ralfs). Surrey! (Ralfs). Sussex EUASTIU'M. 49 Kent ! Hants (zygospores from Xew Forest) ! (Rolfs). Devon! Cornwall! (Ralfs). WALES. — Generally distributed ! i/ SCOTLAND. — Generally distributed zygospores at Sle \vdrum, Aberdeen (Roy fy Bi*sdt). Outer Hebrides ! Orkneys ! Shetlands ! IKELAXD.- -Common. Gfnf^'. -4-27/i; breadth 15-6-20//,; breadth of apex lG'8-14'0 p. ; breadth of isthmus 3'5-4'S p. ; thickness 11'5-14*5 //,. ENGLAND. — Scawfell Pike, Cumberland ! Helvellvii i/ and Blea Tarn, Westmoreland ! Hawkshead, Lan- cashire ! Keighley Moor, W. Yorks ! Bog near Widdale Beck, and Snaizeholme Fell, N. Yorks ! WALES. — Bog above Capel Curig lakes, Grlyder Fach (at 2,200 ft.), Llyn-y-cwm-ifynon, and Llyn Teyrn on Snowdon, Carnarvonshire ! SCOTLAND. — Rhiconich, Sutherland ! Clova, Forfar ! Crianlarich, Perth ! Moidart, Inverness ! W. of Kirk- wall, Orkneys ! IRELAND. — Poisoned Grlen and Lough Nacung, Done- gal ! Achill Island, Mayo ! Xear Oughterard, Galway ! Carrantuohill, Kerry ! G^ot'/i'. Distribution. — Bernese Alps. Greenland. We always find this small Desmid as an inhabitant of upland districts, and it retains its characters very constantly. It has been known for some time past as Cosmarium Sul- reinschii var. Boldtiana Schmidle, differing from typical C. Subreinschii in the larger and broader central protube- rances, in the relatively wider and more angular apices, and in the apical notch. Considering that so far as is known typical C. Subreinscltii does not occur in the British Islands, whereas the Desmid in question is widely distributed and of constant character, we think there is every reason for its specific separation. Not only do we think it is better regarded as a separate species, but we regard the distinct apical emargination, accompanied by a large central protuberance, as characters which must place it in the genus Euastrum. GO BRITISH DESMIDEACE.E. The specific name " Boldtii ; could not be used as it lias already been utilised by Schmidle for a species occurring in Germany, Russia, and Greenland. 36. Euastrum pectinatum Breb. (PI. XXXIX, figs. 10-12.) Heterocarpella pectinata Breb. in Cheval. Microscop. et usage, Paris, 1839, p. 272 (name only). Cosmarium pectinatum Breb. in Menegh. Synops. Desm. 1840, p. 222. Euastmm pectinatum Breb. in Ealfs' Brit. Desni. 1848, p. 86, t. 14, f . 5 a, b, d-f; Arch, in Pritch. Infus. 1861, p. 730, t. 2,f. 10, 30; Eabenh. Flor. Europ. Algar. Ill, 1868, p. 180; Kirchn. Alg. Scliles. 1878, p. 160; Cooke, Brit, Desm. 1886, p. 72, t. 34, f . 5 ; Hansg. Prodr. Algenfl. BOhm. 1888, p. 204 ; De Toni, Syll. Alg. 1889, p. 1068 ; West, Alg. W. Ireland, 1892, p. 138, t. 24, f . 7 ; Alg. Eng. Lake Distr. 1892, p. 723 ; Eoy & Biss. Scott. Desm. 1893, p. 177 ; Nordst. Index Desm. 1896, p. 197 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 65 ; Alg. N. Ireland, 1902, p. 28 ; Scott. Freshw. Plankton, I, 1903, p. 525. Didymidium (Euastrum) pectinatum Eeinsch, Algenfl. Frank. 1867, p. 123. Euastrum pectinatiim forma typica Boldt, Desniid. Gfronland, 1888, p. 6. Helierella pectinata Kuntze, Eevis. gen. plant. 1891, p. 899. Cells of medium size, about 1^- times as long as broad, deeply constricted, sinus narrow and generally slightly open ; semicells three-lobed ; polar lobe dilated, anvil-shaped, angles rounded, apex convexo-truncate and slightly retuse in the middle ; lateral lobes sub- quadrate, deeply retuse at the outer margin, angles acutely rounded ; semicells with three large protube- rances across the broadest part, and with two pro- tuberances within the polar lobe (one on each side). Side view of semicell widely inflated below, then con- stricted and widening out into a dilated subtruncate apex; angles of polar and lateral lobes bilobulate. Vertical view elliptic-oblong, poles bimamillate, with three large rounded-conical protuberances on each side ; polar lobe elliptic oblong, poles bimamillate, and with two rounded-conical protuberances at each side. Cell- wall finely punctate (sometimes almost smooth). Zygospore globose or oblong-ellipsoid, furnished with many elongated, blunt papillae. Length 69-73 ^ ; breadth 44-47 p. ; breadth of polar lobe 32-35 \L ; breadth of isthmus 11*5-12 ^ ; thickness 33-36 /A; cliam. of globose zygosp. without papillae EUA STRUM. Gl 52-57 /x ; length of oblong zygosp. 50-73 //, ; breadth 35-40 (JL; length of pap ill re 3-5 '7 /x. ENGLAND. — Cumberland ! Westmoreland ! (Ralfs). W., N., and E. Yorks (zygospore from Adel Bog, W. Yorks) ! Lancashire! Cheshire (Rolfs). Essex! Surrey (zygospores from Thursley Common) ! Sussex (Rolfs). Kent! Hants! (Rolfs). Wilts! Devon! (Bennett). Cornwall (zygospores from Gumven Moor) ! (Ralfs). WALES. — Generally distributed and often abundant ! SCOTLAND. — Very common ! , zygospores from Slew- drum and Albagie, Aberdeen (Roy $ Bis sett). Outer Hebrides (zygospores not uncommon) ! Orkneys ! Shetlands ! IRELAND. — Common (zygospores from Ballynahinch, Galwav) ! e/ / Geogr. Distribution. — France. Germany. Galicia in Austria. Italy. Xorway. Sweden. Denmark. Bornholm. Finland. Faeroes. Iceland. Greenland. United States. Patagonia (var.). E. pectinatum is very widely distributed in all parts of the British Islands,, but the type form is not so abundant as var. inevolutum. The bluntly-conical protuberances of this Euas- trum are very characteristic and are best seen from the vertical view. The angles of the polar lobe and the upper and lower angles of the lateral lobes are bilobulate,, so that in the vertical view there are two conical protuberances at each pole, both of the lower part of the semicell and of the polar lobe. Thus, the outline in vertical view shows ten protuberances in the lower part of the semicell and eight in the polar lobe. The zygospores are more frequently met with than those of any other Euastrum. i/ Var. inevolutum West & G. S. West (PI. XXXIX, figs. 13-15.) E. pectinatum var. inevolutum West & G. S. West, Freshw. Alg. Ork. and Shetl. 1905, p. 15 (sep.), t. 1, f. 13, 14. Cells a little smaller than in the type ; lateral lobes generally more quadrate, outer margins only slightly retuse ; neck of polar lobe relatively broader and shorter ; apex of polar lobe more convex and retuse in the middle, apical angles more rounded ; protuberances 62 BRITISH DESMIDIACE^:. of lower part of semicell and particularly of polar lobe much reduced (as seen in vertical view). Length 51-63 ju ; breadth 36-42 ^ ; breadth of polar lobe 24-28/1 ; breadth of isthmus 10— ll'5fi ; thickness 21-26 p.. ENGLAND. — More frequent than the type ! WALES. — General in Carnarvonshire ! SCOTLAND. — General and abundant ! IRELAND. — General and abundant ! E. pectinatum forma intermedia Boldt (f Desm. Gronland/ 1888, p. 6, t. 1, f. 3) comes very near this variety, but in Boldt's form the polar lobe is very small and its lateral margins are almost vertical. Boldt does not state whether the protuberances are reduced in his form or not,, whereas this is one of the leading features in var. inevolutum. In the latter variety the angles of the polar lobe and the lateral lobules are broadly truncate or truncate -emarginate in ver- tical view, scarcely bilobulate as in the type. Var. brachylobum Wittr. (PI. XXXIX, fig. 16.) E. pectinatum var. brachylobum Wittr. Gotl. Ol. sotv. Alo-. 1872, p. 48, t. 4, f. 5 ; De Toni, Syll. Alg. 1889, p. 1068 ; Roy & Biss. Scott. Desm. 1893, p. 177. Lobes of semicell broad and very short, margins widely retuse ; semicells with six protuberances, one in the centre, one within the middle of the polar lobe, and one within each angle of the lateral lobes ; poles of vertical view simple and rounded (not emarginate). Length 70 /x; breadth 50 /x; breadth of polar lobe 32/x; breadth of isthmus 15/x; thickness 33/x. SCOTLAND.--" Not so common ' (Roy fy Bissett). Geogr. Distribution . — Sweden. We have never seen any form of E. pectinatum at all approaching var. brachylobnm Wittr. Half s in his ' British Desmids ' describes and figures a form (p. 86, t. 14, f. 5c) which lie calls •'< var. /3." He states that the angles of the polar lobe are slightly emarginate in front view, but it must be remembered that this effect is produced when the cell is in a slightly-oblique position, and his figure undoubtedly gives one the idea that this was the case. KUASTRUM. 63 37. Euastrum gemmatum Breb. (PI. XXXIX, fig. 19.) Cosmarium gemmatum Breb. in Menegh. Synops. Desm. 1840, p. 221. 'r E nostrum papulosum Kiitz. Phyc. germ. 1845, p. 135. Euastrum gemmatum Breb. in Ralfs, Brit. Desm. 1848, p. 87, t. 14, f. 4 Nag. Gatt. einzell. Alg. 1849, p. 120; Rabenh. Flor. Europ. Alg. III. 1868, p. 180 ; Kirchn. Alg. Schles. 1878, p. 160 ; Wolle, Desui. U. S. 1884, p. 101, t. 28, f. 3, 4 ; Cooke, Brit. Desm. 1886, p. 73, t. 35, f. 1 ; Hansg. Proclr. Algenfl. Bohni. 1888, p. 204 ; De Toni, Syll. Alg. 1889, p. 1070 ; West, Alg. W. Ireland, 1892, p. 138 ; Alg. Eng. Lake Distr. 1892, p. 723; Roy & Biss. Scott. Desm. 1893, p. 177; Nordst. Index Desm. 1896, p. 129 ; West & G. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 65 ; Alg. N. Ireland, 1902, p. 28 ; Scott. Freshw. Plankton, I, 1903, p. 525. E. (Eucosmium) Hassallianum Nag. Gatt. einzell. Alg. 1849, p. 121, t. 7 B. E. gemmatum a. typicum Racib. Nonn. Desm. Polon. 1885, p. 94. Helierella gemmata Kuntze, Revis. gen. plant. 1891, p. 898. Cells rather small, almost l^ times as long as broad, very deeply constricted, sinus narrowly linear with a dilated extremity; semicells three-lobecl ; polar lobe short, somewhat cuneiform, with rounded angles and a retuse apex ; lateral lobes subquadrate, lateral margins deeply retuse, angles broadly rounded; semicells with three prominent protuberances across the broadest part, one in the centre, and one within each lateral lobe. Side view of semicell with the lower part widely inflated, then narrowed to form a neck, which widens out, forming a dilated apical portion, apex retuse, apical angles rounded. Vertical view elliptic, with three large rounded protuberances at each side; polar lobe subquadrate (almost cruciform) with deeply retuse sides and rounded angles. Cell-wall finely granulate, granules especially prominent on all the rounded angles and protuberances. Zygospore unknown. Length 48-70 M; breadth 38-47 /z,; breadth of isth- mus 12-14/x; thickness 26-30 ju. ENGLAND. — Cumberland! Westmoreland ! (Rolfs). N. Yorks ! Lancashire ! Sussex (Rolfs). Hants ! (Ealfs). Devon! Cornwall! (Ealfs). WALES. — Capel Curig ! (Cooke fy Wills) and Grlyder Fawr (Roy), Carnarvonshire. SCOTLAND. — Sutherland ! Ross, Inverness, Aberdeen, 64 BRITISH DESMIDIACE.E. Kincardine, Forfar, Perth ! (R»y fy Bt'ssett). Outer Hebrides ! Shetlands ! IRELAND. — Donegal ! Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Geoc/r. Distribution. — France. Belgium. Germany. Gralicia in Austria. Norway. Sweden. Denmark. Bornholm. Poland. S. Russia. Faeroes. Greenland. India, United States. W. Indies. Brazil. Paraguay. E. gemmatiim is one of the prettiest and most characteristic species of the genus. It is widely distributed, but somewhat scarce. 38. Euastrum verrucosum Ehrenb. (PI. XL, fig. 1.) Euastrum verrucosum Ehrenb., 1834 ; Infus. 1838, p. 162, t. 12, f. v ; Ralfs in Ann. Mag. Nat. Hist. 1844, p. 189, t. 6, f. 3; Hass. Brit. Freshw. Alg. 1845, p. 379, t, 91, f . 7 ; Ralfs, Brit. Desm. 1848. p. 79, t. 11, f. 2; Arch, in Pritch. Infus. 1861, p. 728; Rabenh. Flor. Europ. Algar. Ill, 1868, p. 179 ; Delp. Desm. Subalp. 1873, p. 94, t. 6, f . 13-15 ; Kirchn. Alg. Scliles. 1878, p. 160 ; Wolle, Desm. U. S. 1884, p. 100, t. 26, f . 1, 5 ; Cooke, Brit. Desm. 1886, p. 63, t. 31, f . 1 ; Hansg. Prodr. Algeiifl. Bohm. 1888, p. 204 ; De Toni, Syll. Alg. 1889, p. 1066 ; West, Alg. W. Ireland, 1892, p. 136 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott. Desm. 1893, p. 178 ; Nordst. Index Desni. 1896, p. 268 ; West & Gr. S. West, Alg. S. England, 1897, p. 483 ; Alga-fl. Yorks. 1900, p. 65 ; Alg. N. Ireland, 1902, p. 27 ; Scott. Freshw. Plankton, I, 1903, p. 525. E. verrucosum a. typicum Racib. Nonn. Desm. Polou. 1885, p. 94. E. verrucosum a. typicum Boldt, Desni. Gronland, 1888, p. 6. Helierella verrucosa Kuntze, Revis. gen. plant. 1891, p. 899. Cells moderately large, subhexagonal, a little longer than broad, deeply constricted, sinus open for half its length and then narrowly linear; semicellsthree-lobed, interlobular incisions deep but open ; polar lobe widely cuneate, angles rounded and granulate, apex deeply retuse ; lateral lobes wider than polar lobe, cuneate and bilobulate, lower lateral lobule subconical, rounded, granulate and horizontally directed, upper lateral lobule submamillate, granulate, upwardly and outwardly diverging ; semicells with three large protuberances across the broadest part, the central one being the largest, each protuberance furnished with large wart- like granules arranged in concentric circles. Cell-wall O granulate, granules most evident at the angles where EUASTKUM. 65 they are often sharp and conical. Side view of semi- cell widely inflated in the lower part owing to the verrncose central protuberances showing at each side, then narrowed to form a " neck " ; apical portion dilated, angles rounded, apex retuse. Vertical view elliptic, poles mamillate and granulate, with three large sub- verrucose protuberances on each side, upper and lower lateral lobules entire ; polar lobe oblong-rectangular, with retuse sides and rounded angles. Zygospore unknown. Length 93-114 //,; breadth 75-92 /LL; breadth of isthmus 19-22 p. ; thickness 53-55 JJL. ENGLAND.- -Cumberland ! Westmoreland ! (Rolfs). TT. and N. Yorks ! Lancashire ! Leicestershire (Roy). Warwick (Wills). Middlesex (Has sail). Surrey! (Ralfs). Sussex (Rolfs). Kent! (Rolfs). Hants! (Rolfs). Cornwall! (Ralfs). WALES.— Capel Curig ! (Gooke $ Wills), Llyn Ogwen !, Grlyder Fawr (Roy), Carnarvonshire. SCOTLAND.- -Generally distributed ! (Roy § Bissett). Frequent in the plankton ! Shetlands ! IRELAND.- -Donegal ! Mayo ! G-alway ! Kerry ! Dublin and AYicklow (Archer). Armagh ! London- derry ! G-eogr. Distribution. — France. Germany. Galicia in Austria. Hungary. Italv. Xorwav. Sweden. Den- O t/ «. tJ mark. Bornholm. Finland. Poland. TT., Central, and S. Russia. Faeroes. Greenland. Siberia. Japan. India. Australia. Central Africa. United States. Uruguay. Argentina. E. verrucosum is not so abundant as some of the other large species of Euastrnm. It is not often found in bogs, having' a decided preference for the margins of large, reedy ponds and lakes. It cannot easily be confused with any other species of the genus. Var. reductum Norclst. (PI. XL, figs. 2, 3.) E. verrucosum var. reductum Nordst. Alg. et Char. I, 1880, p. 9, t. 1, f . 14 ; De Toni, Syll. Alg. 1889, p. 1067 : West & G. S. West, Alg. N. Ireland, 1902, p. 27 ; Scott, Freshw. Plankton, I, 1903, p. 525. VOL. II. 5 66 BRITISH DESMIDIACE^. Cells rather smaller than in the type; polar lobe subrectangular, angles rounded, apex faintly retuse ; lateral lobes retuse, scarcely bilobulate, angles rounded ; interlobular incisions widely open, subrectangular ; pro- tuberances within the lateral lobes much reduced, scarcely evident in the vertical view ; vertical view of polar lobe rectangular with straight sides. Length 80-89 p. ; breadth 70-86 //, ; breadth of isthmus 18*5-22 JJL ; breadth of polar lobe 29-36 p ; thickness 36-42 p. SCOTLAND. — Plankton of Lochs Tay and Achray, Perth ! Plankton of Loch Ruar, Sutherland ! (J. Murray). General in the plankton in Inverness, Lewis, and Harris, Outer Hebrides ! Plankton of Xeugles * o Water, and of Loch Beosetter, Bressay, Shetlands ! IKELAND.- -Lough G-artan, Donegal ! Geogr. Distribution. — Finmark in Norway. N". Russia. United States. Uruguay. Argentina. Var. coarctatum Delp. (PL XL, fig. 4.) E. verrucosum var. coarctatum Delp. Desm. snbalp. 1873, p. 95, t. 6, f . 16 ; Racib. Nonn. Desm. Polon. 1885, p. 94, t. 13, f. 11 ; De Toni, Syll. Alg. 1889, p. 1067 ; West, Alg. W. Ireland, 1892, p. 136 (forma). Cells slightly smaller than in the type, sinus gene- rally more closed ; polar lobe prominent, exserted, apex only slightly retuse ; lateral lobes scarcely bilobulate, widely retuse. Length 92*5-97 p,; breadth 85-87 //, ; breadth of polar lobe 31-35 p.; breadth of isthmus 20-23 p. IRELAND.- -Derryclare Lough, Galway ! Geogr. Distribution. — Galicia in Austria. Poland. Italy. A form of this variety is figured in which the upper angles of the lateral lobes are much reduced, and the polar lobe appears still more prominent ; length 90 /UL ; breadth 76 JJL ; breadth of polar lobe 32*5 /u; breadth of isthmus 21 /u (PL XL, fig. 5). This form was originally figured in West, ( Alg. W. Ireland/ 1892, t. 20, f. 11. EUASTROI. 67 Var. alatum Wolle. (PI. XL, fig. G.) E. ver.'ucosum var. alatum Wolle, Desm. U.S. 1884. p. 101, t. 26, f. 4 ; De Toni, Syll. Alg. 1889, p. 1067 ; Anderss. Sverio-. Chlor. 1890, p. 10 ; Gutw. Flor. Gloii. Okolic Lwowa, 1891, p. 72 ; West, Alg. W. Ireland, 1892, p. 136. Cells with the outer half of the sinus open and then partially closed again, causing the basal angles of the semicells to have a hooked appearance. Length 84-110 /x; breadth 71-108 /x; breadth of isthmus 22 ft;, thickness -11 p.. SCOTLAXD. — Tarbert, Harris, Outer Hebrides ! IRELAND. — Cloonee Lough, Kerry ! Geogr. Distribution. — Gralicia in Austria. Sweden. X. Russia. United States. Var. planctonicum West & Gr. S. West. (PL XL, fig. 7.) E. verrucosum var. jolanctonicum West & G. S. West, Scott. Freshw. Plankton, I, 1903, p. 537, t. 15, f. 4. Cells with a widely open sinus ; lateral lobes entire, obtusely conical. Length 90 /x ; breadth 91 /x; breadth of isthmus 19*5 /x. SCOTLAXD. — In the plankton of Lochs Ruar and Xan Cuinne, Sutherland ! (.7. Murray). This remarkable variety occurred plentifully in the plankton of Loch Ruar. A few specimens were observed in which there was a slight indication of the presence of the superior lateral lobules. 39. Euastrum occidentale West & Gr. S. West. (PL XXXIX, fig. 20.) ? Cosmarium protractum Wolle, Desrn. U.S. 188-1, p. 83, t. 17, f. 27, 28 [not C. protractum (Nag.) De Bary, 1858]. Euastrum verrucosum Ehrenb. var. simplex Josh. New and Rare Desm. 1885, p. 34, t. 254, f . 2 ; West, Alg. N. Wales, 1890, p. 287. E. verrucosum Ehrenb. var. simplex Josh, forma tumescens Turn. Freshw. Alg. E. India, 1893, p. 74, t. 11, f. 9*. E. occidentale WTest & G. S. West, Some Desm. U.S. 1898, p. 293. Cells of medium size, about 1J times longer than broad, deeply constricted, sinus narrowly linear with a dilated apex ; semicells truncate-pyramidate, broadly 68 BRITISH DESMIDIACEJK. rounded (very slightly subrectangular), superior part of lateral margins retuse, apex somewhat protracted, convex-truncate and retuse-emarginate in the middle, superior angles rounded. Side view of semicell ovate- truncate. Vertical view elliptic, poles slightly angular, with a very slight inflation at the middle on each side. Cell-wall finely granulate, granules much reduced in the centre of the semicells, and quite absent at and just below the apical emargination, often with an arc of larger granules in the middle of the semicells about o o two-thirds the length from the base. Zygospore unknown. Length 85-89 p, (rarely only 65 p.) ; breadth 71-72 p, (rarely only 60 fi) ; breadth of apex 33-3 7 ^ (rarely only 27 ft) ; breadth of isthmus 20 p. ; thickness 36-42 p.. WALES.- -Llyn Coron, Anglesey ! Geogr. Distribution. — Canada. United States. We have only once observed this Euastrum from the British Islands, but have examined numerous specimens from Nova Scotia, Maine, and Massachusetts. Fig. 20, PL XXXIX, is the first accurate figure of this Desmicl published, and so that there should be no doubt as to its identity the drai'-'nuj w«.y made from one of Joshua's original specimen*. Borge (' Alg. erst. Regnell. Expecl./ II, Desmid. 1903, p. 99) suggests a relationship between E. occidentals and Cosma- rium Turpinii Breb., but the latter is considerably smaller, with two small central protuberances, and without an emargi- iiate apex. We know C. Turpinii very well, as it is frequent in some parts of the British Islands, and it never has such a protracted apex as E. occidentals. E. Occident ale has very little in common with E. verr-ucosum. For the reasons for adopting the specific name "occidentale ; consult West & G. S. West, ' Some Desm. U.S.' 1898, p. 293. 40. Euastrum insular e (Wittr.) Roy. (PI. XL, figs. 11-13.) Euastrum binale (Turp.) Ehrenb. var. insulare Wittr. Gotl. Ol, s<">tv. Alg. 1872, p. 49, t. 4, f. 7; Arch, in Quart. Journ. Micr. Sci. 1873, p. 434 ; Cooke, Brit. Desm. 1886, p. 76, t. 35, f. 10 ; De Toni, Syll. Alg. 1889, p. 10S5 ; West, Alg. W. Ireland, 1892, p. 140 ; Johns. Bare Desm. U. S. 1894, p. 286, t. 211, f. 8. E. insulare (Wittr.) Koy in Scott. Naturalist, April 1877 ; July, 1883 ; Eoy & Biss. Scott. Desm. 1893, p. 177 ; West & G. S. West, Alg. S. EUASTEUM. 69 England, 1897, p. 4S4 ; Alga-fl. Yorks. 1900, p. Go ; Chlorophy. Koh Chang, 1901, p. 85 ; Alg. N. Ireland, 1902, p. 2U ; Freshw. Alg. Ceylon 1902, p. 15G. Cosmarium insnlare (Wittr.) Schmiclle, Chlorophy-Fl. Torfstiche Virn- heim, 1S94, p. 59. Cells minute, 1-J- times longer than broad, deeply constricted, sinus narrowly linear, with a dilated ex- tremity ; semicells three-lobed, interlobular incisions subrectangular ; polar lobe widely rectangular, angles rounded, apex truncate and retuse-emarginate in the middle ; lateral lobes short, basal angles subrectangular, sides slightly retuse. Side view of semicell ovate, with O i/ . • a slight protuberance on each side. Vertical view elliptic, with a very slight protuberance at the middle on each side. Cell- wall smooth. Zygospore unknown. Length 17'5-30/x; breadth 1 1-5-22 //,; breadth of isthmus 3*3-6 ft ; thickness 9'5-11'Ofi. ENGLAND. — Westmoreland! (Bissett). N. Yorks! Lincolnshire ! Cambridgeshire (Wicken Fen) ! Hants ! (Rot/). Devon ! Cornwall (Bennett). WALES. — Llyn Bodrie, Anglesey ! Frequent in Carnarvonshire ! SCOTLAND.- -Sutherland ! Ross ! Inverness, Aber- deen, Kincardine, Forfar, Perth !, Argyll (Roy $ Bissett). Outer Hebrides! IRELAND.- -Xear Grlenties, Loughs Anna and Akibbon, Donegal ! Lower Lake of Killarney, Kerry ! Dublin and Wicklow (Archer). Lough Derryadd, Armagh! (ii'nijr. Distribution. — Galicia in Austria. Norway. Sweden. Siam. United States. This small and characteristic species is widely distributed and sometimes occurs in abundance. It was originally described as a variety of Euastmm binale, but the distinctly three-lohed semicells and the rectangular basal angles suffi- ciently characterize it. A form of it was described from Cambridgeshire (vide G. S. West, 'Alga-fl. Cambr/ 1899, p. 114, t. 396, f. 11) in which the lateral lobes were less rectangular and almost *_j bilobulate. Length 28 /UL ; breadth 19 /t • breadth of isthmus 5 M; thickness 11 /UL (PL XL, fig. 14). 70 BRITISH DESMIDIACE.E. 41. Euastrum crassangulatum Borg. (PL XXXIX, fig. 17.) Euastrum crassangulatum Borg. Desiii. Brasil. 1891, p. 37, t. 3, f. 25. Cells minute, 1-ir times longer than broad, deeply constricted, sinus narrowly linear; semicells quadrate- pyramidate, angles slightly rounded, basal angles sub- rectangular, upper part of lateral margins retuse, apex broadly truncate and retuse-emarginate in the middle ; semicells with a protuberance in the centre, and a smaller one within each basal and apical angle. Side view of semicell broadly ovate, upper part of lateral margins slightly retuse, apex truncate. Vertical view elliptic, with a slight protuberance at the middle on each side. Cell-wall thickened at all the angles of the semicells. Zygospore unknown. Length 27 p, ; breadth 18 /x ; breadth of isthmus 5 /*; thickness 13 p.. Geoc/r. Distribution. — Austria (var.). Brazil. The typical form is not known to occur in the British Islands. Var. ornatum West. (PI. XXXIX, fig. 18.) E. crassangulatum var. ornatum West, Alg. W. Ireland, 1892, p. 141"), t. 20, f. 16. Semicells with 5 granules around the central pro- tuberance and one in the middle, and with 6 others at regular intervals within the margins. Length 27 /x; breadth 17'5jn; breadth of isthmus 4*5 JJL ; thickness 14 p.. IRELAND.- -Ballynahinch, G-alway ! 42. Euastrum Cornubiense sp. nor. (PL XL, fig. 8.) Cells minute, about 1-J- times longer than broad, very deeply constricted, sinus narrowly linear with a dilated extremity ; semicells three-lobed, incisions between the •/ •' ' EUASTRUM. 71 lobes widely subrectangular ; polar lobe broadly rect- angular, angles rounded, apex convex with a strong median thickening; lateral lobes short, angles rounded, outer margins retuse ; semicells with a central papillate protuberance. Side view of semicell elliptic, with an acute papilla at the middle on each side. Vertical view elliptic, with an acute papilla at the middle on each side. Cell-wall smooth and slightly thickened at the base of all the sinuations. Zy go spore unknown. Length 24 ^ ; breadth 1 5 JJL ; breadth of isthmus 3*8 JJL; thickness 11 '5 /x. EXGLAXD. — Xear Senens, Cornwall ! This species forms one of the connecting links between the genera Euastrum and Cosmarium. There is no actual emar- gination of the apex of the semicells, although there is a thickened internal ridge occupying its place. It might equally well be called Cosmarium Cornubiense West & Gr. S. West. 43. Euastrum crassicolle Lund. (PL XL, figs. 9, 10.) Euastrum crassicolle Lund. Desm. Suec. 1871, p. 23, t. 2, f. 8; West, Alg. X. Wales, 1890, p. 288 ; Boy & Biss. Scott. Desm. 1893, p. 176 ; Xordst. Index Desm. 1896 ; West & G-. S. West, Alga-fl. Yorks. 1900, p. 65. E. crassicolle a. typicum Racib. Nonn. Desni. Polon. 1885, p. 91. Helierella crassicollis Kuntze, Eevis. gen. plant. 1891, p. 898. Cells minute, about twice as long as broad, deeply constricted, sinus narrowly linear ; semicells truncate- pyramidate, almost three-lobed ; polar lobe prominent, wide, slightly dilated, angles rounded, apex emarginate ; lateral lobes very short, somewhat bilobulate with rounded angles. Side view of semicell oblong-pyra- midate, apex truncate, lateral margins towards the base biundulate. Vertical view elliptic, poles truncate, and with a broad inflation at the middle on each side. Cell- wall smooth. Zygospore unknown. Length 24'5-28/x; breadth 13'5-15/x; breadth of isthmus 5'2-8'5/x; thickness 9*5-11 p. EXGLAXD.— Mickle Fell, X. Yorks ! 72 BRITISH DESMIDIACE.E. WALES. — Capel Curig and Llyn Padarn, Carnarvon- shire ! Dolgelly, Merioneth ! SCOTLAND. — Poolewe, Ross ; Presswhin and Bog- wartle in Cromar, and Glen Ey, Aberdeen ; Canlochan, Forfar; Eannoch, Perth (Roy fy Bissett). Craig an Lochan, Perth ! New Galloway, Kirkcudbright ! IRELAND. — Dublin and TVicklow (Archer). Geogr. Distribution. — France. Galicia in Austria (var.). Norway. Sweden. Poland. X. Russia. Nova Zembla. Spitzbergen. Greenland. United States. The side view of this species easily distinguishes it from any other Euastrum. It seems to be chiefly a northern species. 44. Euastrum crispulum (Xordst.) nob. (PL XL, figs. 15-18.) Euastrum sublobatum Breb. var. crispidum Xordst. Norges Desni. 1873, p. 10, t. 1, f . 9 ; De Toni, Syll. Alg. 1889, p. 1042 ; West & G>. S. West, Welw. Afric. Freshw. Alg/1897, p. 113. E. pyramidatum West, Alg. W. Ireland, 1892, p. 139, t. 20, f. 13 (figures not good) ; Alg. Eng. Lake Distr. 1892, p. 723 ; N-ordst. Index Desm. 1896, p. 215 ; West & G. S. West, Alg. S. England, 1897, p. 484 ; Some Desm. U. S. 1898, p. 287, t. 16, f. 14. ? E. liinale (Turp.) Ehrenb. var. elonyatum Liitkem. Desm. Attersees, 1892, p. 559, t. 8, f. 11. Cells minute, about 1-J- times longer than broad, deeply constricted, sinus narrowly linear with a dilated extremity ; semicells pyramidate-truncate, basal angles rounded, with a slight undulation above the basal angles, upper part of lateral margins retuse ; apex widely truncate, distinctly emarginate in the middle, that part on each side of the apical emargination dis- tinctly retuse, apical angles acutely rounded. Side view of semicell ovate, slightly narrowed near the rounded apex. Vertical view elliptical with a broad inflation at each side. Cell-wall smooth. Zygospore unknown. Length 25-28 p. ; breadth 16-20 p. ; breadth of apex 9-11 /x; breadth of isthmus 3'5-7'5 /x; thick- ness 12*5-15 p.. ENGLAND. — Loughrigg, Westmoreland ! Thursley Common, Surrey ! Withiel, Cornwall ! KCASTKOJ. 73 SCOTLAND. — Rhiconich, Sutherland ! Lewis, Outer Hebrides ! IRELAND . — Ballynahinch, Kylemore, and Eoundstone, Gal way ! Geogr. Distribution. — Norway. W. Africa. United States. The Desmid we described from Ireland as Euastrum pyramidatum is identical in every respect with that described by Nordstedt from Norway as Euastrum sublobatum var. crispulum. It is a very constant species, easily distinguished from E. sublobatum, and we have therefore placed it as Euastrum crispulum . It is smaller than E. sublobatum, the semicells are pyra- midate (not quadrate), and the undulations above the basal angles and the undulated character of the apex are features which are never present in E. sublobatum. In the vertical and side views the central inflation of E. crispulum appears very much smaller than that of E. sublobatum. 45. Euastrum sublobatum Breb. (PL XL, fig. 19.) Euastrum sublobatum Breb. in Ealfs' Brit. Desm. 1848., p. 91, t. 32,, f . 4 ; Nordst. Index Desru. 1896, p. 245. Cosmarium sublobatum (Breb.) Arch, in Pritch. Infns. 1861, p. 731 ; Kabenh. Flor. Europ. Algar. Ill, 1868, p. 168; Kirchn. Alg. Scliles. 1878, p. 152 ; Wolle Desm. U.S. 1884, p. 80, t. 18, f. 21, 23 ; Cooke, Brit. Desrn. 1886, p. 79, t. 36, f . 1 ; De Toni, Syll. Alg. 1889, p. 1041 ; West. Alg. Eng. Lake Distr. 1892, p. 723 ; West and G. S. West, Alga-fl. Yorks. 1900, p. 90; Alg. X. Ireland, 1902, p. 32. r.-sinella sublobata Kimtze, Eevis. gen. plant. 1891, p. 925. Cells small, about 1-J- times as long as broad, deeply constricted, sinus narrowly linear with a widely-dilated extremity ; semicells snbquadrate, lateral margins retuse, basal angles rounded, superior angles more acutely rounded, apex convex-truncate, retuse-emar- D-inate in the middle. Side view of semicell ovate, o with a large protuberance on each side near the base, upper part of lateral margins retuse, apex rounded; vertical view elliptic, with a large protuberance in the middle on each side, giving it a subcruciform appear- ance. Cell- wall smooth. Zygospore unknown. /4 BRITISH DESMIDIACE^. Length 26-5-48 //,; breadth 20-39 //,; breadth of apex 19-26 jn; breadth of isthmus 5 "2-1 2*5 //,; thick- ness 18-21 /x. ENGLAND.- -Borrowdale and Scarf Gap Pass, Cumber- land! Westmoreland! (Rolfs). Ogden Clongh, Peny- ghent, Oughtershaw Tarn, and Cautley Spout, W. Yorks ! WALES. — Bettws-y-coed, Twll Du, and Llyn Teyrn on Snowdon, Carnarvonshire! Dolgelly, Merioneth (Ralfs). SCOTLAND. — Sutherland !, Ross, Inverness, Aberdeen, Kincardine, Forfar, Perth, Argyll (Roy fy Bissett). IRELAND.- -Lough Fea, Londonderry! Dublin and Wicklow (Archer). Geogr. Distribution. — France. Germany. Galicia and Austria. Hungary. Italy. Norway. Poland. S. Russia. Greenland. New Zealand (var.). United States. W. Indies. Paraguay (var.). We think this Desmici is better regarded as a species of Euastrum rather than of Cosmarium on account of the retuse- emarginate apex of the semi-cells, with which is associated a relatively large central protuberance. It is essentially an upland species. Var. dissimile Nbrdst, (PL XLV, fig. 7.) Cosmarium snblobatum (Breb.) Arch, subsp. dissimile Nordst. Desm. Ital. 1876, p. 39, t. 12, f. 15. Cells less deeply constricted, the breadth of the isthmus being about two-thirds that of the cell. Angles of semicells dissimilar ; in vertical view with the superior angles truncate and the inferior angles retuse. Side view of semicell broadly truncate-pyramidate, with a small basal tumour. Length 26-28*5 ^; breadth 17-20/x; breadth of isthmus 12-13 JJL ; thickness 13-14 ^. SCOTLAND.- -Loch Luichart, Boss ! ICELAND.- -Dublin and Wicklow (Archer). Geogr. Distribution. — Italy. Var. subdissimile var. nov. (PL XL, fig. 20.) Cells with a broader isthmus ; semicells with larger KUASTEUM. 75 basal angles, the retuse portion of the lateral margin being nearer the apex; apex "widely convex and retuse- emai'O'inate in the middle. Side view of semicell o quadrate-pyramidate, inferior and superior angles rounded, sides and apex retuse. Vertical view oblong- rectangular, angles rounded, poles retuse, with a pro- minent protuberance at the middle on each side ; polar lobe rectangular, angles round, sides and poles retuse. Length 34*5 p,; breadth 22 p, ; breadth of apex 18 ft : breadth of isthmus 9*5 ^ ; thickness 17 /*. SCOTLAND. — Near Tarbert, Harris, Outer Hebrides ! This variety somewhat resembles the previous one, but the general outline of the semicells is rather different, and the side and vertical views differ greatly in the amount of the retuseness of the poles. 46. Euastrum validum West and Gr. S. West. (PI. XL, figs. 21, 22.) Euastrum validum West and G. S. West, Some X. Anier. Desm. 1896, p. 245, t. 14, f. 32, 33 ; Freshw. Alg. Ceylon, 1902, p. 156. Cells minute, 1-g- times longer than broad, very deeply constricted, sinus narrowly linear with a dilated extre- mity ; semicells truncate-pyramidate, lateral margins retuse. inferior angles inflated, superior angles some- what rounded and sometimes slightly thickened ; apex broad, truncate-convex, einarginate and thickened in the middle; semicells with a small papilla within each basal angle, a large granule in the middle, close to the isthmus, and a small scrobiculation near the centre. Side view of semicell ovate, with a granule near the isthmus on each side; vertical view elliptic, with a small papilla on either side of each pole. Cell- wall smooth. Zygospore unknown. Length 26-5-30 /*; breadth 19-22 p.; breadth of apex 13*5-14'5 //,; breadth of isthmus 4'4-4'5/x ; thick- ness 10—11 p. SCOTLAND. — Rhiconich, Sutherland! Loch Diracleet, near Tarbert, Harris, Outer Hebrides ! Geogr. Distribution. — Ceylon. United States. 76 BRITISH DESMIDIACE^B. This species is on the border-line between the genera Euastrum and Cosmarium, but we are inclined to retain it in the former genus on account of the distinctly emarginate apices. It has two near relatives in Cosmarium subbinale (Nordst.) Lagerh. and C. miedzyrzecense Eichl. & Gutw., neither of which are known to occur in Britain. NOTE. — In his 'Freshw. Alg. Eng. Lake Distr./ 1886, Bennett figures very roughly a Desmid which he terms " Euastrum crenatum Kiitz/5 His short description and his outlined figure do not agree, however, with Kiitzing's descrip- tion of E. crenatum. What Bennett's plant was we do not know, neither is the information he gives concerning it of sufficient value to establish a species. It seems to us that it might possibly be a form of Cosmarium tetragonum Nag. Genus 14. MICRASTERIAS Ag., 1827. Ag. in Flora, 1827, p. 642. Menegh. Synops. Desm. 1840, p. 214. Ralfs, in Ann. Nat. Hist. 1844, p. 259. Hass. Brit. Freshw. Alg. 1845, p. 385. Ralfs, Brit. Desm. 1848, p. 68. De Bary, Conj. 1858, pp. 39, 40, 47, 50, 70. Arch, in Pritch. Infus. 1861, pp. 720, 725. Rabenh. Flor. Etirop. Alg. Ill, 1868, p. 187. Wolle, Desm. U.S. 1884, p. 108. < Cooke, Brit. Desm. 1886, p. 53. Hansg. Prodr. Algenfl. Bohm. 1888, p. 207. De Toni, Syll. Alg. 1889, p. 1109. (jr. S. West, Treatise Brit. Freshw. Alg., 1904, p. 165. Cells of variable size, often large, usually a little longer than broad, sometimes subcircular in general outline, usually much compressed, very deeply con- stricted in the middle, sinus usually linear (open outwards in several species) ; semicells subsemicircular, usually five-lobed (in some species three-lobed) ; polar lobe generally widely cuneate, emarginate, or widely notched ; lateral lobes usually bilobulate, lobules generally slightly bilobed ; median part of base of semicells generally without protuberances ; vertical view elliptic-lanceolate or linear-lanceolate ; one lobed chloroplast in each semicell, with many scattered pyrenoids. MIC'RASTEKIAS. 77 Zygospores globose, radially ornamented with stout spines, either simple, bifid, trifid, or quadrifid at their apices. This genus includes some of the handsomest of British Desmids, many of the species being' remarkable for the elegance of the tabulation of the semicells. There is always an odd number of lobes to each semicell, the middle one being differentiated from the rest as the polar Lobe. Many of the species are flattened and disc-shaped, the cells beino- relatively much thinner than, in any other g'enus i_j tJ t/ O of Desmids. Certain species connect this genus both with Euastrum and Xantlndliini. Micrasterias and Euastrum were both included by Kuntze in his genus " Helierella," but we have previously mentioned that this name cannot be used for a genus of Desmids. Species of this genus generally occur intermingled with other Desmids, and some of them are only found in the very richest localities for these plants, being confined to the lakes and bog's of the Older Palaeozoic and Precambrian areas. O There are 18 British species, which can be arranged as follows : SECTION A. (Holocystis Hassall.) Polar lobe entire ; lateral lobes of seniicells two, transversely placed, generally entire, and attenuated to their extremities. 1. M. oscitans. 2. M. pinnatifida. SECTION B. (Actinocystis Turner.) Polar lobe with a median incision of variable depth (rarely almost absent) ; lateral lobes of semicells four, radiately disposed, and widening outwards. a. Lateral lobes o-enerallv much divided : interlobular i incisions narrow. f Interlobular incisions not deep. 3. M. truncata. 4. M. crenatit. 5. If. Jenneri. 6. M. conferta. ft Interlobular incisions deeper. 7. M. papillifero. 8. M. Murrayi 9. M. Sol. 10. M. apiculato. 11. M. rotata. 12. M. denticidata. 13. M. verrucosa. 14. M. Tliomasianii. 78 BRITISH DESMIDIACEJE. /3. Lateral lobes with, fewer divisions ; interlobular in- cisions widely open. 15. M. radiata. 16. M. Crux-Melitensis. SECTION C. Polar lobe with accessory processes ; lateral lobes of semicells two, symmetrical or asymmetrical. 17. M. Americana. 18. M. Mahdbuleshwarensis. 1. Micrasterias oscitans Ralfs. (PL XLI, figs. 1-4.) Micrasterias ? oscitans Ealfs in Jemier's Flora Tunbridge Wells, 1845, p. 198 ; Ralfs, Brit. Desm. 1848, p. 76, t. 10, f . 2 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 189; Wille, Gorges Ferskv. Alg. 1880, p. 21, t. 1, f. 4, 5 (fonnae) ; Wolle, Desm. U.S. 1884, p. 116, t. 33, f. 3, 4; De Toni, Syll. Alg. 1889, p. 1110; Eoy & Biss. Scott. Desm. 1893, p. 174. Holocystis oscitans, Hass. Brit. Freslrw. Alg. 1845, p. 387, t. 90, f . 4 ; Bennett, Freshw. Alg. Eng. Lake Distr. 1886, p. 7, t. 1, f. 7-10. Euastrum (Micrasterias) oscitans Nag. Gatt. einz. Alg. 1849, p. 123. Tetrachastrum oscitans, Dixon in Proc. Dnbl. Nat. Hist. Soc. 1859 ; p. 205 ; also in Quart. Jonrii. Micr. Sci. 1859, p. 83. Helierella oscitans Kuntze, Kev. gen. plant. 1891, p. 899. M. oscitans a typica Turn. Freshw. Alg. E. India, 1893, p. 88. Cells of medium size, about as long as broad, deeply constricted, inner half of sinus usually narrowly linear, outer half open and acutely conical ; semicells three- lobed ; polar lobe wide, fusiform or subfusiform, with acuminate (rarely bifid) poles and a convex apex ; incisions below the polar lobe deep and somewhat widely open ; lateral lobes horizontal, ovate-triangular, with minutely bifid extremities. Side view of semi- cell elliptic-pyramidate, with a rounded apex. Vertical view elliptic-fusiform, with acuminate (very rarely bifid) poles. Cell-wall minutely punctate. Zygospore unknown. Length 125-146 ^ ; breadth 123-135 /*; breadth of polar lobe 91-95 p; breadth below polar lobe 52-56 p\ breadth of isthmus 24-26 JJL ; thickness 44-52 p.. ENGLAND.- -Kirk Fell, Cumberland ! Westmoreland (Ralfs). Sussex (Ralfs). Chobham Common, Surrey ! WALES.- -Capel Curig (Oooke $* Wills) and Moel Siabod !, Carnarvonshire. Dolgelly, Merioneth (Rolfs). MiCRASTEKIAS. 79 SCOTLAND. — Aberdeen (P. Grant). IRELAND. — Glencar, Kerry (Archer). Gecxjr. Distribution. — France. Germany. Austria (forma). G-alicia (forma). Xorway. Denmark. United States. Typical j\I. oscitans is exceedingly rare and we have only found it on three occasions. Fig. 4 (on PI. XLI) is a drawing of a semicell from Kirk Fell, Cumberland, which agrees very well with the plant as described by Ralfs. American specimens have been described by Wolle with a diameter (breadth) of 150-160 /.*. Var. mucronata (Dixon) Wille. (PL XLI, figs. 5, (3.) Tetrachastrum mucronatum Dixon in Proc. Dubl. Nat. Hist. Soc. 1859, p. 204, t. 1, f . 5-8 ; in Quart. Journ. Micr. Sci. 1859, p. SI, t. 7 ; Arch. in Pritcli. Infus. 1861, p. 725. llicrasterias mucronata (Dixon) Rabenh. Flor. Europ. Alg. Ill, 1868, p. 187 ; Kirchn. Alg. Schles. 1878, p. 163 ; Cooke in Grevillea, 1881, p. 89, t. 141, f. 2 (in part) ; Cooke, Brit. Desm. 1886, p. 53, t. 20, f. 1 ; De Toni, Syll. Alg. 1889, p. 1112 ; West, Alg. N. Wales, 1890, p. 286 ; Alg. W. Ireland, 1892, p. 133 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott. Desm. 1893, p. 174; Xordst. Index Desm. 1896, p. 177 ; West & G. S. West, Alg. S. England, 1897, p. 484. M . oscitans Ealfs var. mucronata (Dixon), Wille, Norges Ferskv. Alg. 1880, p. 21, t. 1, f. 3 ; Turn. Freshw. Alg. E. India, 1893, p. 88 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 65. Helierella mucronata Ktintze, Revis. gen. plant. 1891, p. 899. Cells proportionately longer than in the type, with the sinus more closed ; lateral lobes larger and some- what inflated, lateral angles generally furnished with two blunt teeth, and often with a third tooth above those at the angles ; polar lobe flattened at the apex, and sometimes broadly retuse, lateral angles down- wardly curved and generally furnished with a single v O -0 fJi. SCOTLAND.- -Glen Urquhart, Inverness; Upper Pow- lair in Birse, Birsemore Loch, Dalwhing near Aboyne, near Loch Dawan, and near Loch Kinord, Aberdeen ; Muiryhaugh and Dalbrake in Strachan, Kincardine; Glen* Coe, Argyll ; Xorth Glen Sannox, Arran (Eoij fy Bissetfy. Xear Stirling! Ehiconich, and plankton of Loch Morar, Sutherland ! Xear Tarbert and in the plankton of Loch Laxadale, Harris ! Xear Balallan and in plankton of Loch Mor Bharabhais, Loch Cuthaig, and Loch Fadaghoda, Lewis, Outer Hebrides ! Geogr. Distribution.- -France. Xorway. Sweden. Finland. Greenland. United States. This Micrasterias is essentially of a northern type and it is one of the rarest British species. In Europe it seems to be almost confined to the north-western countries,, and it is met with frequently in the eastern parts of the United States. It is only known from Scotland in the British Islands, having1 been found in a number of localities on both the ^j eastern and western slopes. In some parts of the Outer Hebrides it can be obtained frequently, "but never in abundance. J/. conferta is a very characteristic species, 3/. papillifera being the only other species of the genus with which it could be confused. It is, however, easily distinguished hy the shortness and breadth of the polar lobe, which widens out from a relatively narrow base. The lohes and lohules are more compact and crowded than is generally the case in 31. papillifera, and the incisions between them are not so deep. The apex of the polar lobe also differs greatly from that of M. papillifera, and the interlobular incisions are not bordered hy minute spines. Irregularities in the form of the lobules are of frequent occurrence. The four small lohules of each lateral lobe should 90 BRITISH DESMIDIACE^. normally be slightly retuse or emarginate, but they are often truncate with a median papilla, or even bluntly triangular. There is also a great tendency for the lateral lobes to grow in size until they not only overlap each other at the sinus, but also overlap the polar lobe on each side. Var. hamata Wolle. (PL XLIII, figs. 10, 11.) M. conferta var. hamata Wolle, in Bull. Torr. Bot. Club, 1883, p. 19, t. 27, f . 1 '; Desrti. U. S. 1884, p. 114, t. 53, f. 12, 13 ; West & G. S. West, Some N. Amer. Desni. 1896, p. 241, t. 14, f. 8, 9. M. hamata Borg. Desm. Bras. 1890, p. 31. Lateral lobes as in the typical form, or rarely some- what further subdivided; polar lobe less widely cuiieate, with the lateral angles downwardly uncinate. Length 80-128 ^ ; breadth 75-107 ^ ; maximum breadth of polar lobe 3 6' 5-53 ^ ; breadth of isthmus 10-5-19 p. SCOTLAND. — Plankton of Loch nan Cuimie, Suther- land ! (J. Murray). K"ear Tarbert, Harris, Outer Hebrides ! Geogr. Distribution. — United States. This is a very curious variety of M. conferta in which the lateral margins of the polar lobe are greatly excavated just below the angles of the lobe. The lobe is thus more or less anvil-shaped, and the angles are distinctly uncinate. The incisions below the polar lobe are therefore widely open, but closed again at the outer extremity.' Specimens of this variety sometimes reach a larger size than is ever attained by the typical form. We have already pointed out (' Some N". Amer. Desm./ p. 241) that Borgesen. was greatly in error in elevating this variety to the rank of a species. Moreover, the Micrasterias which Borgesen figured from Brazil under the name of " M. hamata forma Brasiliensis ' (vide Borg. ' Desm. Bras/ t. 2, f. 11) is certainly not a form of M. conferta var. hamata. We have seen many specimens of M. conferta which combined the characters o£ both the type and the var. hamata. Very often the polar lobe of one semicell is typical, whereas that of the other semicell is such as is found in the var. hamata. We give a figure of one of these forms which demonstrates con- clusively that the var. hamata is truly a variety of- AT. conferta and not a distinct species (PL XLIII, fig. 9 ; length 77 ^t ; breadth 76 MICEASTEEIAS. 91 7. Micrasterias papillifera Breb. (PI. XLIY, figs. 1, 2, 7.) Micrasterias papillifera Breb. in Ealfs' Brit. Desm. 1848, p. 72, t. 9, f . 1 ; Arch, in Pritch. Infus. 1861, p. 727, 1. 1, f. 18, 19 ; Eabenh. Flor. Europ- Alg. Ill, 1868, p. 194 ; Delp. Desm. snbalp. 1873, p. 86, t. 4, f . 5, 6 ; Kirchn. Alg. Schles. 1878, p. 163 ; Wolle, Desm. U. S. 1884, p. 109, [t. 32, f . 8, 9 ?] ; Cooke, Brit. Desin. 1886, p. 60, t. 27, f . 2 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 210 ; De Toni, Syll. Alg. 1889, p. 1132 ; West, Alg. N. Wales, 1890, p. 287 ; Alg. W. Ireland, 1892, p. 135 ; Alg. Eng. Lake Distr. 1892, p. 722; Eoy & Biss. Scott. Desm. 1893, p. 174; Nordst. Index Desm. 1896, p. 194 ; West & G. S. West, Alg. S. England, 1897, p. 484 ; Alga-fl. Yorks. 1900, p. 66 ; Alg. N. Ireland, 1902, p. 30. Didymidium (Micrasterias} papHliferum Eeinsch, Algenfl. Frank. 1867, p. 146. Helierella papillifera Knntze, Eevis. gen. plant. 1891, p. 899. Cells of moderate size, usually a little longer than broad, subelliptic or subcircular, deeply constricted, sinus very narrowly linear ; semicells 5-lobed, with the lobes and lobules usually almost approximate, inter- lobular incisions linear ; polar lobe cuneate with con- cave sides, apex concave with a slight median notch, each angle slightly produced and furcato-emarginate, with a pair of small teeth on each side of the median notch ; lateral lobes cuneate, of almost equal breadth, each divided by a moderately deep incision into two lobules, lobules again divided, the four ultimate divi- sions of each lobe being emargmate (or rarely tridenti- culate). Side view of semicell elliptic-oblong, with a tricuspidate apex. Vertical view narrowly oblong with subacute poles. Cell-wall generally minutely punctate, with a row of acute granules or denticula- tions on each side of the sinus and the interlobular incisions ; in both side and vertical views these granules or small teeth are marginal. Zygospore globose, furnished with strong processes, each of which is doubly furcate at the apex, the ulti- mate divisions being small but widely spreading ; the processes are one-third the diameter of the zygospore in length. Length 1 18-145 ^; breadth 108-145 ^ ; breadth of polar lobe 35-44 ^ ; breadth of isthmus 15-22/*; thickness 21-24 /i; diam. zygosp. without processes 92 BRITISH DESMIDIACEJE. 42-44 p, with processes 67-72 /A; length of processes 15-17*5 /I. ENGLAND. — Cumberland! Westmoreland! (Rolfs). W. and N. Yorks ! Lancashire! Warwick (Wills). Surrey ! (Ralfs). Sussex (Ralfs). Hants ! (Rolfs). Devon ! Cornwall ! (Ralfs). WALES.- -Fairly general in the north ! Zygospore from Dolgelly, Merioneth (Ralfs). SCOTLAND. — Greneral ! Zygospores from Dinnet, Aberdeen, and from Fowlis Wester, Perth (Rot/ fy Bissett). Outer Hebrides ! Orkneys! Shetlands ! IRELAND.- -Donegal ! Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Antrim ! Geoc/r. Distribution. — France. Germany. Austria and Gralicia. Hungary. Italy. Norway. Sweden. Denmark. Bornholm. Finland. 1ST. and S. Russia. Russian Lapland. Greenland. New Zealand. United States. Brazil. This is the most abundant of the smaller British species of the genus which possess deeply-lobecl semicells. It is known at once by the form of the polar lobe and by the denticula- tions bordering the interlobular incisions. It is somewhat variable in its relative proportions. Most specimens are a little longer than broad, but individuals are sometimes met with of equal length and breadth. M. papillifera cannot be confused with M. conferta if the polar lobe is carefully examined. It must likewise be remembered that the latter species is smaller, very much rarer, and more restricted in its distribution. Some forms occasionally exhibit a roughness on the exte- rior of the cell-wall somewhat similar to that commonly present on M. Jenneri. Cells of this kind are invariably old ones and may exhibit a rather corroded outline. Schmidle ('Beitv. alp. Alg./ 1896, p. 23 cum fig.) has named forms of this nature which he found in the Austrian Tyrol " var. verrucosa.' Forma major. (PI. XLIV, fig. 3.) Length 200 /JL; breadth 170 //,; breadth of polar lobe 51 /JL; breadth of isthmus 29 p. WALES. — Llyii Ogwen, Carnarvonshire ! MICEASTERIAS. 93 Var. glabra Norclst, (PI. XLIV, figs. 4, 5.) M. papillifera Breb. var. glabra Norclst. in Wittr. & Noi'dst. Alg. Exsic. 1882, No. 466; in fasc. 21 (1889), p. 35; West Alg. W. Ireland, 1892, p. 135. Cells destitute of the acute granules or denticula- tions which are normally present on both sides of the principal incisions. Length 90-125 p; breadth 88-109 p.; breadth of isthmus 19 /x. SCOTLAND.- -Near Tarbert, Harris, Outer Hebrides ! IRELAND. — Ballynahinch, G-alway ! Geogr. Distribution. — X. Russia. Brazil. A form of this variety was described from the west of Ireland as "var. glabra Nordst. forma inflata "West," in which there was a small basal inflation in the side view of the semi- cells. This form is figured on PI. XLIV, fig. 5 (length 125 /LI • breadth 125 /u; breadth of isthmus 15 fi ; thickness 29 p). Consult West, ' Alg. W. Ireland/ 1892, p. 135, t, 20, f. 10. Nordstedt has suggested that this form is possibly a small speci- men of M. denticulata var. not at a, but we do not think so. Var. varvicensis Turner. (PL XLIY, fig. 6.) M. papillifera Breb. var. varvicensis Turner, Desm. Notes, 1893, p. 345, fig. 13. " A variety with the lobes and lobules incised almost as in M. Crux-Melitensis." The interlobular incisions are considerably more open than in the typical form. Length 128 /*; breadth 120 /x; breadth of isthmus 26 p,. ENGLAND. — Button Park, Warwick (T. Bolton). 8. Micrasterias Murrayi "West & Gr. S. West. (PL XLV, %s. 1-3.) Micrasterias Murrayi West & G. S. West, Scott. Freslrw. Plankton, I, 1903, p. 538, t. 15, figs. 1, 2. Cells of medium size, as broad as long, very deeply constricted, sinus widely open with an acute apex; semicells broadly subsemicircular and deeply 5-lobed, 94 BRITISH DESMIDIACE^E. with the incisions between the lobes widely open and subradial; polar lobe with subparallel sides, suddenly dilated near the apex, which is retusely emarginate, angles emarginate- dentate, with a minute tooth within the apical margin towards each angle ; lateral lobes equal, divided into four equal lobules, the median incision being twice the depth of the other two incisions, each lobule emarginate-dentate. Cells with a series of minute teeth or denticulations on each side of the interlobular incisions and the sinus. Zygospore unknown. Length 142-151 /A; breadth 142-147 p; breadth of isthmus 18 jut. SCOTLAND. — In the plankton of Loch Ruar, Suther- land ! (/. Murray). This species occurred in abundance in the plankton of Loch Ruar, the only locality from which it has yet been obtained. Its characters are very constant and do not agree with those of any other described species of the genus. The incisions between the lobes and lobules are all widely open with concave sides, which feature causes them to be widest about the middle. The sinus, which is more open than that of any other incised Micrasterias, is one of the most striking charac- ters of the species. The only species with which it could be confounded are M. papillifera Breb. and M. Sol (Ehrenb.) Kiitz. (particularly var. ornata Nordst.). From M. papillifera it is distinguished by the widely-open sinus and incisions, which are also deeper, and by the very different form of the polar lobe. It is dis- tinguished from M. Sol by the widely-open sinus and incisions, which are not so deep, and by the absence of the further subdivision of the superior lateral lobes. M. Miirrayi possesses a series of minute denticulations along the margins of the sinus and each of the incisions between the lobes. This character is present in M. papillifera and in M. Sol var. ornata. Var. triquetra West & G. S. West. (PI. XLV, fig. 4.) M. Miirrayi var. triquetra West & G. S. West, Scott. Freshw. Plankton, I, 1903, p. 538, t. 15, f. 3. Cells triquetrous, triradiate in the vertical view. MICRASTEEIAS. 95 Length 163 /x; breadth 151 /x; breadth of isthmus, 16 fji. SCOTLAND. — In the plankton of Loch Doon, Ayr- shire ! This variety is of great interest as only one other triangular form of Micrasterias is known to occur, viz. M. pinnatifida (Kiitz.) Ralfs var. trigona West (' Freshw. Alg. Maine/ 1889, p. 206; in ' Journ. Bot./ 1889, t. 291, f. 15). 9. Micrasterias Sol (Ehrenb.) Kiitz. (PL XLVI, figs. 1, 2.) Euastrum Sol Ehrenb., Verbreit. imd Einfhiss mikroskop. Lebens in Siid- iind Nord-amerika, Physik. Abh. Preuss. Ak. Wiss. zu Berlin, 1841 (Berlin, 1843), p. 413, t. 4, f. 16. Hicrasterias radiosa Ealfs, Brit. Desm. 1848, p. 72, t. 8, f. 3; Arch, in Pritch. Infus. 1861, p. 727, t. 1, f. 21 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 192; Delp. Desm. subalp. 1873, p. 85, t. 4, f. 2-4; Wolle, Desm. U.S. 1884, p. 109, t. 31, f. 2, 3 ("figures badl ; Cooke, Brit. Desm. 1886, p. 59, t. 27, f. 1; De Toni, Syll. Alg. 1889, p. 1133; West, Alg. W. Ireland, 1892, p. 134; Eoy & Biss. Scott. Desm. 1893, p. 174; Nordst. Index Desm. 1896, p. 219 ; West & G-. S. West, Alg. S. England, 1897, p. 484 ; Scott. Freshw. Plankton, I, 1903, p. 525. M. Sol (Ehrenb.) Kiitz. Spec. Alg. 1849, p. 171; Jacobs. Desm. Danem. 1875, p. 188. Helierella Sol (Ehrenb.) Kuntze Eev. gen. plant, 1891, p. 897. Cells approximately circular in outline, very deeply constricted, sinus slightly open with each margin faintly 2- or 3-undulate ; semicells deeply 5-lobed, with the incisions between both the lobes and lobules deep and slightly open, sometimes open inwards but closed outwards ; polar lobe with subparallel sides, slightly expanded at the apex, apical margin retuse- emarginate, each angle emarginate-dentate, with a small tooth attached within the apical margin near the angle on each side ; lateral lobes unequal, superior lateral lobes slightly larger than inferior lateral lobes and generally (but not always) more subdivided; in- ferior lateral lobes divided into four equal lobules by three incisions, the median one being much deeper than the other two, each lobule furcate-dentate at the extremity (or sometimes further divided into two fur- t/ \ cate-dentate portions of equal size) ; superior lateral 96 BRITISH DESMIDIACE^E. lobes divided into eight equal lobules by seven incisions of which the median one is much the deepest, each lobule furcate-dentate at its extremity ; margins of interlobular incisions generally slightly undulate like the sinus. Side view of semicell linear-oblong, very »' gradually attenuated to a tridentate apex. Vertical view linear-fusiform, with acute poles and a slight flat- tened protuberance in the middle on each side. Cell- wall delicately punctate. Zygospore unknown. Length 162-191 p.; breadth 158-192 p; breadth of polar lobe (at apex) 36-38 p.; breadth of isthmus 17-18 /i. ENGLAND. — Bowness, Westmoreland ! Near Chapel Wood, S.E. Surrey! Cornwall (Marquand). WALES. — Capel Curig, Carnarvonshire (Gooke ^ Wills) \ Llyn Grwernan near Dolgelly, Merioneth (Ralfs). SCOTLAND.- -Slewdrum, Aboyne and Birsemore Lochs, Aberdeen (Roy £f Bissett). Rhiconich, and in the plankton of Lochs Shin, Grhriama, and nan Cuinne, Sutherland ! Plankton of Loch Fadaghoda, Lewis ; near Tarbert, Harris ; and in the plankton of Loch nan Eun, N. Uist, Outer Hebrides ! Plankton of Loch Beosetter, Br essay, Shetlands ! «/ • IRELAND. — Lough Derryclare, G-alway ! Adrigole, Kerry ! Geogr. Distribution. — France. Italy. Sweden. Den- mark. United States. Jamaica. Brazil. This is one of the most beautiful species of the genus and has been recorded principally under the name of "Micras- terias radiosa." The first recognizable mention of this Micrasterias is that by Ehrenberg in 1843 under the name of Euastrum Sol. Neither Ecliinella radiosa Acharius (in Weber and Mohr, 'Beitr. zur Naturkunde/ II, 1810, p. 340, t. 4, f. 4-15), nor Ecliinella radiosa, Lyngbye (' Tantamen Hydrophyt. Danicse/ etc., Hafnias, 1819, p. 208, t. 69, f. E) refer to anything of the nature of a Micrasterias as the genus is at present understood. Micrasterias radiosa Ag. (in c Flora/ 1827, p. 643) is simply a MICEASTEEIAS. 97 name which the author gave to Echinella radiosa Lyngbye. Micrasterias radiosa Ralfs (' Brit, Desm/ 1848, p. 72, t. 8, f. 3) which that author wrongly attributed to Agardh, is the first good account of the Desmid described and figured by Ehrenberg five years previously (1843) under the name of " Euastrum Sol.3' Ralfs himself recognized this identity and placed Euastrum Sol Ehrenb. as a synonym of his Micras- terias radiosa. The specific name "Sol" must therefore take precedence over Ralfs' name "radiosa." Micrasterias Sol is almost circular in outline, and is easily distinguished by the depth and elegance of its lobulation. The margins of the deeper incisions are usually slightly undulate and the lobules frequently overlap. North American specimens of this species exhibit much greater variation than is shown in British examples. Var. ornata Nordst, (PI. XL VI, figs. 3, 4.) Micrasterias radiosa Ralfs var. ornata Xordst. Desm. Brasil, 1870, p. 223, t. 2, f. 11 ; Lund. Desm. Suec. 1871, p. 13 ; Roy & Biss. Scott. Desm. 1893, p. 174 ; West & G-. S. West, Some N". Amer. Desm. 1896, p. 240. M. Sol (Ehrenb.) Kiitz. var. ornata Nordst. in Pointsfor. Skand. Vaxt. iv, 1880, p. 25. AVith a row of minute teeth or deiiticulations on each side of the sinus and of the incisions between the five lobes of the semicells. Length 112-188 p.; breadth 110-171 /A; breadth of isthmus 16-18 ^', thickness 22 p.. WALES. — Capel Curig, Carnarvonshire ! SCOTLAND. — Near Brin, Inverness; Slewdrum and near Craigendinnie Farm, Aberdeen; Scolty Dam, Kincardine (Roy fy Bissett}. Plankton of Loch Doon, Ayrshire ! Plankton of Loch Fadaghoda, Lewis, Outer Hebrides ! Geogr. Distribution. — Norway. United States. Brazil. 10. Micrasterias apiculata (Ehrenb.) Menegh. (PI. XL VII, figs. 1, 2.) Euastrum apiculatum Ehrenb., 1834 ; Infus. 1838, p. 161, t. 12, f . II. Micrasterias apiculata (Ehrenb.) Menegh. Synops. Desm. 1840, p. 216; VOL. II. 98 BRITISH DESMIDIACEJE. Ealfs, Brit. Desm. 1848, p. 209 ; Arch, in Pritch. Infus. 1861, p. 727 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 193 ; Kirchn. Alg. Schles. 1878, p. 163 ; Eoy & Biss. Jap. Desm. 1886, p. 193, t. 268, f . 13 ; Cooke, Brit. Desm. 1887, p. 186, t. 48, f. 1 ; Nordst. Bornh. Desm. 1888, p. 187 ; Heimerl, Desm. alp. 1891, p. 602 ; West & G. S. West, Some N. Amer. Desm. 1896, p. 240 ; Nordst. Index Desm. 1896, p. 48. Didymidium (Micrasterias) apiculatum Eeinsch, Algenfl. Frank. 1867, p. 145. Micrasterias fimbriata Ealfs forma apiculata Wolle, Desm. U. S. 1884, p. 110. Helierella apiculata Ktintze, Eev. gen. plant. 1891, p. 898. Cells large, a little longer than broad, subelliptic in outline, very deeply constricted, sinus widely open out- wards but linear towards its apex ; semicells 5-lobed ; polar lobe distinctly exserted, lower portion with sub- parallel sides, upper portion widely dilated, apex retuse- emarginate, angles with a pair of diverging spines and with a large curved spine on the apical margin close to each angle, and with a pair of spines on each side of the apical notch ; lateral lobes subequal, bilobulate, lobules again divided and each division furnished with two (sometimes three) marginal curved spines ; incisions bordering the polar lobes opening widely outwards, the remaining incisions (both primary and secondary) more or less open. Side view narrowly ovate-pyramidate with a truncate apex bearing spines. Vertical view rhomboid-elliptic with acute poles. Cell- wall furnished with numerous minute spines, arranged in subradiate rows or scattered over the surface, with four rather larger spines arranged in a quadrate manner in the middle of each semicell just above the isthmus. Zygospore unknown. Length 220-294 /i; breadth 180-250 p.; breadth of isthmus 30-36 /x,. ENGLAND. — Bowness, Westmoreland (Turner}. Geogr. Distribution. - - France. Germany. Galicia in Austria. Italy. Sweden. Denmark. Bornholm. Finland. Poland. Russia. Japan. India. Burma. United States. This beautiful species in its typical form is only known from the English Lake District, having been found by Turner in a locality which furnishes numerous specimens of MICEASTERIAS. 99 several of its varieties. It can be at once recognized by the numerous spines inserted regularly on the margins of the lobules and polar lobe, and more or less irregularly all over the surface of the cell. It is somewhat variable in its relative proportions. Var. fimbriata (Ralfs) Nordst. (PL XL VI, fig. 6 ; PL XL VII, figs. 3, 4.) Euastrnm Rota Ehrenb. Inftis. 1838 (in part), t. 12, f. Id. Micrasterias fimbriata Ealfs, Brit. Desna. 1848, p. 71, t. 8, f . 2 ; Arch, in Pritch. Iiifus. 1861, p. 727 ; Eabenh. Flor. Eur. Alg. Ill, 1868, p. 193 ; Kirchn. Alg. Scliles. 1878, p. 162 ; Wolle, Desm. "U. S. 1884, p. 109, t. 36, f. 1-8 "(various forms) ; Cooke, Brit. Desm. 1886, p. 59, t. 26, f. 1 ; Wolle, Freshw. Alg. U. S. 1887, p. 338 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 210; De Toni, Syll. Alg. 1889, p. 1131; Roy & Biss. Scott. Desm. 1893, p. 174 ; Nordst. Index Desm. 1896, p. 124. Didymidium (Micrasterias) fimbriatum Eemscli. Algenfl. Frank. 1867, p. 149. Micrasterias apiculata (Ehrenb.) Menegh. stibsp. fimbriata Nordst. Boriih. Desm. 1888, p. 190 ; West, Alg. Eng. Lake Distr. 1892, p. 722 ; Nordst. Index Desm. 1896, p. 48 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 66. Helierella fimbriata Kuntze, Revis. gen. plant. 1891, p. 898. Interlobular incisions narrower than in the type, causing the lateral and polar lobes to become approxi- mate ; polar lobe less projecting, usually with fewer apical spines ; cell-wall commonly destitute of surface- spines. Zygospore globose, furnished with slender, elongate, scattered spines, mostly furcate at their extremities and sometimes notched below the middle ; furcate extremities with the divisions recurved. Length 230-255 p.; breadth 216-245 p. ; breadth of isthmus 29-32 p ; diam. of zygospore without spines 75 ju,, with spines 125 /x. ENGLAND. — Bowness, Westmoreland ! Cullingworth, Aclel Dam, and Eldwick, W. Yorks ! Sutton Park, Warwick (Wills). WALES.- -Capel Curig, Carnarvonshire (Cooke fy Wills). Dolgelly, Merioneth (Rolfs). SCOTLAND. - - Scotston Moor, near Kintore, Press- whin, Loch Ullachie, and near Ballater, Aberdeen ; near Bridge of Feugh, Kincardine ; Meiimuir, Forfar (Hoy $ Bissett). Khiconich, Sutherland ! Plankton of Loch nan Cuinne, Sutherland ! (/. Murray). 100 BRITISH DESMIDIACEJE. IRELAND. — Dublin and "\Yicklow (Archer}. Clough, Antrim ! Geogr. Distribution. — France. Belgium. Germany. Galicia in Austria. Norway. Sweden. Denmark. K". and S. Russia. United States. Var. fimbriata forma spinosa Bissett. (PI. XL VII, fig. 5.) M . fimbriata Ealfs var. spinosa Bissett in Roy & Biss. Scott. Desm. 1893, p. 174, t. 4, f. 3. Cell-wall furnished with a row of minute spines along each side of the principal incisions, three or four close to the base of each semicell, and a row of about four under the base of the polar lobe. Length 210 p. ; breadth 200 /x ; breadth of isthmus, ^dO fJi. SCOTLAND. — Slew drum, Loch Ullachie and marsh west of it, Aberdeen (Roy fy Bissett). M. apiculata var. fimbriata, although a scarce Desmid, is more often met with than any of the other forms of J/. apicu- lata. It is exceedingly variable in the form of the lobules, especially those of the inferior lateral lobes nearest the sinus, which often project considerably beyond the general contour of the cell. The polar lobe is also variable in the amount of its exsertion, sometimes projecting considerably beyond the superior lateral lobes, sometimes not projecting in the least degree. The insertion of the marginal spines is precisely similar to that in typical M. apiculata. Most forms of M. apiculata var. fimbriata are usually destitute of surface- spines, but many intermediate stages are met with between such forms and the thickly-spined form of M. apiculata itself. In some the surface-spines are scattered and few in number, in others they are irregularly disposed in the neighbourhood of the principal incisions, and in others they are more numerous and more regularly arranged. The latter form was named by Bissett "/. spinosa" The zygospore is recorded from Rochester, New Hampshire, U.S.A., by Wolle. MICRASTER1AS. 101 Var. brachyptera (Lund.) nob. (PL XL VI, fig. 5 ; PI. XL VII, figs. 6, 7.) .V. brachyptera Lund. Desm. Suec. 1871, p. 12, t. 1, f. 4; Wolle, Desm. U.S. 1884, p. 110, t. 32, f. 6, 7 ; Biss. Desm. Windermere, 1884, p. 192 ; Cooke, Brit. Desni. 1886, p. 63, t. 30, f. 2; De Toni, Syll. Alg. 1889, p. 1120. If. brachyptera forma bispinata Turn. New and Rare Desm. 1885, p. 937, t. 16, f. 15. If. apiculata (Ehreiib.) Menegli. subsp. fimbriata y brachyptera Nordst. Bornh. Desm. 1888, p. 190. Helierella brachyptera Kuntze, Revis. gen. plant. 1891, p. 898. Proportionately longer than the type; polar lobe more projecting, relatively larger and wider, with a distinct constriction below the apex, apical margin widely retuse ; lateral lobes shorter and generally with fewer lobulations ; sinus and incisions between the lobes widely open, especially the incisions between the polar lobe and the superior lateral lobes; generally with a row of spines bordering each side of the polar lobe and the sinus. Cell-wall punctate. Length 191-230 p.; breadth 131-180 //,; breadth of isthmus 34-37 ft,; max. breadth of polar lobe 54-60 p.; thickness 72 p. ENGLAND. — Bowness, Westmoreland! (Bissett). SCOTLAND. - - Loch Ness, Inverness ! Rhiconich, Sutherland ! Plankton of Loch Fadaghoda, Lewis, Outer Hebrides ! Geoyi'. Distribution. — Norway. Sweden. Poland (form). S. Russia. United States. This is a well-marked variety of J/. apiculata differing in its shorter lateral lobes, wider and more outstanding polar lobe, and in the fewer number of surface-spines. The inser- tion of the marginal spines is exactly similar to that of all other forms of J\I. apiculata, and the lobulation of the lateral lobes and number of inserted spines is very variable, the two semicells of one individual often differing considerably in these respects. There is thus no reason for Turner's name "forma bispinata." Most specimens of this variety possess a row of spines within each side of the polar lobe and within each margin of the sinus. The number of these spines is variable and in some specimens they are entirely wanting. 102 BKITISH DESMIDIACE^. The latter forms have been termed by Nordstedt " forma glabriuscula' (vide PL XL VII, fig. 7). The lateral lobes in some forms are widely separated and spreading, but in others they are more compact and the incision between them is narrow. 11. Micrasterias rotata (G-rev.) Ralfs. (PL XL VIII, figs. 1-6.) Micrasterias furcata Ag. in Flora, 1827, p. 643 [Description bad and quite unrecognizable ; Agardh's original specimens have been found to be partly M. rotata']. ? Euastrum Rota Ehrenb. Entwick. Lebends. d. Infus. 1832, p. 82 [Descrip- tion bad and too brief] ; Ehrenb. Infus. 1838, p. 161, 1. 12, f. 1 [Figures include M. rotata, M. apiculata var. fimbriata, and M. truncata']. Echinella rotata G-rev. in Hooker's Brit. Fl. 1833, II, p. 398. Cosmarium stellinum Corda in Aim. de Carlsbad, 1834, p. ISO. Eutomia rotata Harv. Man. Brit. Alg. 1841, p. 187. Micrasterias rotata (Grev.) Ralfs in Ann. Mag. Nat. Hist. 1844, p. 259, t. 6, f . 1 ; Hass. Brit. Freshw. Alg. 1845, p. 385, t. 90, f . 1 ; Kalfs, Brit. Desm. 1848, p. 71, t. 8, f. 1 a (and 6 ?) ; Arch, in Pritch. Infus. 1861, p. 727, t. 1, f . 20 ; in Quart. Journ. Micr. Sci. 1868, p. 294 ; Kabenh. Flor. Europ. Alg. Ill, 1868, p. 108 cum fig. xylogr. ; Lund. Desm. Suec. 1871, p. 12 ; Delp. Desm. subalp. 1873, p. 82, t. 4, f . 1 ; Kirchn. Alg. Schles. 1878, p. 162 ; Wolle, Desm. U.S. 1884, p. 109, t. 34, f . 1, 2 ; Cooke, Brit. Desm. 1886, p. 57, t. 24; Hansg. Prodr. Algenfl. Bohm. 1888, pp. 209, 253; De Toni, Syll. Alg. 1889, p. 1126; West, Alg. N. Wales, 1890, p. 286 ; Alg. W. Ireland, 1892, p. 134 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Eoy & Biss. Scott. Desm. 1893, p. 174 ; Nordst, Index Desm. 1896, p. 226 ; West & G. S. West, Desm. Singapore, 1897, p. 163 ; Alg. S. England, 1897, p. 484 ; Alga-fl. Yorks. 1900, p. 66 ; Alg. N. Ireland, 1902, p. 30 ; Scott. Freshw. Plankton, I, 1903, p. 525. Didymidium (Micrasterias) rotatum Eeinsch, Algenfl. Frank. 1867, p. 149. Helierella rotata Kuntze, Kevis. gen. plant. 1891, p. 899. Micrasterias rotata var. acutidentata Benn. Freshw. Alg. S.W. Surrey, 1892, p. 9, t. 2, f. 10 [Figure incorrect]. Cells large, a little longer than broad, subcircular in outline, very deeply constricted, sinus narrowly linear ; semi cells 5-lobed, interlobular incisions narrowly linear; polar lobe gradually widening upwards, with concave sides, often slightly projecting, apex retuse-emarginate, angles slightly produced and bidentate ; lateral lobes unequal and broadly cuneate, each divided into two lobules by a deep incision ; superior lateral lobes larger than inferior lobes, each lobule subdivided into four equal emarginate (or bidentate) parts by three incisions, the median one being the deepest ; lobules of inferior lateral lobes divided into two (sometimes four) MICRASTERIAS. 103 bidentate (rarely tridentate) parts. Side view of semicell ovate-lanceolate, with a broadly truncate apex and an inflated base. Vertical view narrowly elliptic -rhomboid, with acute poles and a small in- flation in the middle of each side. Cell-wall delicately punctate. Zygospore globose, furnished with many strong, elongate, simple spines. Length 208-366 /*; breadth 165-305 p.; breadth of isthmus 29-43 ^ ; breadth (maximum) of polar lobe 48-80 jit ; diam. zygospore without spines 108 IJL, with spines 158 p.. ENGLAND. — Cumberland ! Westmoreland (up to 2,400 ft, on Helvellyn) ! (Balfi). W. and K Yorks ! Lancashire ! Leicestershire (Roy). Warwick (Wills). Gloucestershire (Balfs). Wilts ! Surrey ! (Rolfs). Sussex (Balfs). Kent ! (Balfs). Hants ! (Bennett). Devon! (Bennett). Cornwall! (Balfs). WALES. — Capel Curig! (Cooke $• Wills), Llyn Padarn! Llyn Idwal !, T Foel Fras !, Carnarvonshire. Glamor- ganshire ! SCOTLAND. — General ! Zygospores from Slewdrum, Aberdeen ; near Bishop's Dam, Kincardine ; Monroman Moor, Forfar (Boy fy Bissett). Occasional in the plankton ! Outer Hebrides ! Shetlands ! IRELAND. — General, but scarce ! Zygospores from Wicklow (Archer). Geogr. Distribution. — France. Germany. Austria. Galicia. Hunsfary. Italv. Norway. Sweden. Den- ~ «/ «/ i/ mark. Bornholm. Finland. Poland. S. and Central Russia. Japan. India. Siam. Singapore. United States. Brazil. M. rotata is not a common species, although very widely distributed. It is easily distinguished from M. denticulata by the emarginate-dentate lobules and by the polar lobe, which is slightly exserted and furnished with bidentate angles. The principal variation is in the polar lobe, especially in the amount of its exsertion. Sometimes the incisions on each side of the polar lobe are more or less open, and 104 BRITISH DESMIDIACE.E. its angles may be produced to form very short bidentate processes. The inferior lateral lobes occasionally possess the same number of ultimate lobules as the superior lateral lobes, and in more normal specimens in which the inferior lateral lobes are only subdivided into four divisions, some or all of these divisions are sometimes tridentate. Forma graimlata West. M. rotata forma granulata West, Alg. W. Ireland, 1892, p. 134. Cell-wall distinctly granulate, granules flattened and irregularly scattered. IRELAND. — Lough Aunierin, Galway ! Forma evoluta Turn. M. rotata forma evoluta Turn. Freshw. Alg. E. India, 1893, p. 167, t. 23, f. 1. M. rotata var. pulchra Lemm. Zweiter Beitrag zur Algenflora des Ploner Seengebietes, Forschungsberichte Biol. Stat. Plon, iv, 1896, p. 173, fig. 7. Incisions between the lobes and lobules more open than in the type ; polar lobe furnished with a pair of small teeth on the apical margin on each side of the median emargination. Length 270-282^; breadth 220-262^. SCOTLAND. — Sligachan in Skye, Inverness ! Geocjr. Distribution. — Germany. India. The polar lobe of this form may or may not be exserted, and the cell-wall is sometimes strongly punctate. Var. urnigera Bennett. M. rotata var. urnigera Benn. Freshw. Alg. Hamps. and Devon, 1890, p. 6, t. 1, f. 9. Slightly larger than the type ; polar lobe " urn-like' and projecting for a distance of 25 p.. Length (including projecting polar lobe) 325 /n ; breadth 250 p,. ENGLAND. — Lyndhurst, Hants (Bennett). We are unacquainted with this variety, and have not reproduced Bennett's figure, as it is too much of a caricature. MICRASTERIAS. 105 12. Micrasterias denticulata Breb. (PI. XLIX, figs. 1-7 ; PI. L, figs. 1, 2.) Micrasterias denticulata Breb. Alg. Falaise, 1835, p. 5-4, t. 8 ; Ralfs, Brit. Desm. 1848, p. 70, t. 7, f . 1 ; De Bary, Conj. 1858, p. 41 ; Arch, in Pritch. Infus. 1861, p. 727, t. 2, f . 22 ; in Quart. journ. Micr. Sci. 1867, p. 296 ; 1. c. 1868, p. 294 ; Rabenh. Flor. Europ. Alg. Ill, 1868, p. 108, cum fig. xylogr. ; Lund. Desm. Suec. 1871, p. 12 ; Jacobs. Desni. Danem. 1875, p. 186, t. 7, f. 11, t, 8, f. 1 ; Kirchn. Alg. Schles. 1878, p. 162; Gay, Monogr. loc. Conj. 1884, p. 52, t. 1, f . 2, 3 ; Wolle, Desm. U. S. 1884, p. 109, t. 34, f. 4-8 [forms] ; Cooke, Brit. Desm. 1886, p. 56, t. 22 ; Hausg. Prodr. Algenfl. Bohni. 1888, p. 209 ; De Toiii, Syll. Alg. 1889, p. 1130; West, Alg. N. Wales, 1890, p. 286; Alg. W. Ireland, 1892, p. 134 ; Alg. Eng. Lake Distr. 1892, p. 722 ; Roy & Biss. Scott. Desm. 1893, p. 174 ; Nordst. Index Desm. 1896, p. 99 ; West & G. S. West, Alg. S. England, 1897, p. 484; G. S. West, Variation Desm. 1899, p. 384 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 66; Alg. X. Ireland, 1902, p. 30. Didymidium (Micrasterias} denticulatum Reinsch, Algenfl. Frank. 1867, p. 147. Micrasterias furcata Ag. var. denticulata Rabenh. Flor. Europ. Alg. Ill, 1868, p. 192. Helierella denticulata Eomtze, Revis. gen. plant. 1891, p. 898. Cells large, about 1-g times longer than broad, broadly elliptic in outline, deeply constricted, sinus narrowly linear ; semicells 5-lobed, interlobular in- cisions narrowly linear ; polar lobe narrowly cuneate, with dilated apex and concave sides, not projecting beyond the lateral lobes, apical margin retuse with a widely-open notch in the centre, angles obtuse or sometimes truncate emarginate ; lateral lobes almost equal and broadly cuneate, superior lateral lobes some- times a little larger than inferior ones, divided into two lobules by a deep incision, each lobule further divided into four (sometimes only two) subequal, retuse or emarginate parts. Side view of semicell narrowly pyramidate, with a marked protuberance on each side near the base. Vertical view fusiform, poles acutely conical, with three undulations at the middle on each side. Cell-wall delicately or sometimes coarsely punctate. Zygospore globose, furnished with scattered, elon- gate, stout spines with bifid and trifid apices, some of which sometimes divide again and become recurved. Length 205-350 /* ; breadth 1 77-277 /u; breadth of 106 BEITISH DESMIDIACE.E. isthmus, 23-40 /n ; breadth (maximum) of polar lobe 55-75^; thickness 55-60 ^ ; diam. of zygospore with- out spines 80-116 //,, with spines 170-195 /A. ENGLAND. — Cumberland! Westmoreland! (Rolfs). AY. and N. Yorks ! Lancashire! Cheshire (Roy). Leicestershire (Roy). Warwick (Wills). Gloucester- shire (Rolfs). Wilts ! Surrey (zygospores from Thursley Common) ! Sussex (Ralfs). Kent! (Ralfs). Hants! (Rolfs). Devon! (Bennett). Cornwall! (Raffs); zygospores from Halgavor Moor ! WALES.— General ! Up to 2,200 ft. on Glyder Fach, Carnarvonshire ! SCOTLAND. • - General ! (Roy § Bissett). Up to 8,500 feet on Lochnagar ! Scarce in the plankton ! Outer Hebrides ! Shetlands ! IE ELAND. --General ! Geogr. Distribution. — France. Germany. Austria. Galicia. Hungary. Italy. Norway. Sweden. Denmark. Bornholm. Finland. N., Central, and S. Russia. Faeroes. Greenland. Japan. India. Sumatra. Aus- tralia. Xew Zealand. United States. Brazil. M. denticulata is a common British species, and is more often met with than any other species of the genus except M. truncata, the latter being more plentiful at elevations of 1,000 feet and upwards. It can sometimes be obtained in pure gatherings in small boggy ditches or at a boggy spring. Such pure collections we have made at Eldwick and Adel in W. Yorkshire. The ordinary form of M. denticulata is a little smaller than M. rotata, the lateral lobes are more equal and equally lobed, and their ultimate subdivisions are truncate-e margin ate and not bidentate. The polar lobe is not exserted beyond the periphery of cell as in M. rotata, is more cuneate in shape, with a deeper median notch, and possesses rounded or rounded-truncate angles. In the side-view of the semicell M. rotata is stouter and more turgid than M. denticulata, and in the vertical view it is also stouter with a solitary rounded protuberance on each side, whereas M. denticulata is more slender in vertical view and possesses three less-elevated pro- tuberances at the middle on each side. MICRASTEEIAS. 107 Var. angulosa (Hantzscli) West & G. S. West, (PL L, figs. 3, 4.) Micrasterias angulosa Hantzscli in Eabenh. Alg. no. 1407, 1862; Nordst. Desm. Gronl. 1885, p. 10 ; Cooke, Brit. Desm. 1886, p. 62, t. 29 ; Nordst. Freshw. Alg. N. Zeal, and Austral. 1888, p. 29, 78 ; De Toni, Syll. Alg. 1889, p. 1133 ; Eoy & Biss. Scott. Desm. 1893, p. 172, t. 4, f. 2. Didymidium (Micrasterias) angulosum (Hantzscli) Eeinscli, Algenfl. Frank. 1867, p. 147, t. 8, f. 2. Helierella angulosa Kimtze, Eevis. gen. plant. 1891, p. 898. Micrasterias denticulata Breb. var. angulosa (Hantzscli) W. & Gr. S. West, Alg. N. Ireland, 1902, p. 30. Cells more angular than in the type, often relatively broader near the poles ; lateral lobes only divided by primary and secondary incisions, the four subdivisions being truncate with rounded ano'les. retuse, or retuse- o o emarginate. Cell- wall distinctly and densely punctate. Zygospore very similar to that of the type. Length 210-282 //,; breadth 184-230 /I; breadth of isthmus 30-33 p. ; thickness 54 p. ; cliam. of zygospore without spines 114-116 /x; length of spines 32 /x. ENGLAND. — Westmoreland ! (Bissett). Lancashire ! W. Yorks ! Warwick (Wills). Thursley Common, Surrey ! Hants ! (Roy). Cornwall (Marquand). WALES.- -Capel Curig (Cooke $ Wills) and Rhyddu!, C arnarvonshire . SCOTLAND.- -Sutherland !, Eoss !, Inverness, Aber- deen, Kincardine, Forfar !, Perth !, Argyll ; zygo- spores from Slewdrum, Aberdeen (Pot/ ^* Bissett}. IRELAND. — Lough Akibbon, Donegal ! Near Ough- terard, Galway ! Slieve Donard, Down ! Dublin, Wicklow, and Westmeath (Archer). Geogr. Distribution. — France. Germany. Galicia in Austria. Norway. Sweden. Denmark. Bornholm. Greenland. New Zealand. This variety lias been regarded by some authors as a species,, but the distinctions between it and M. denticulata are too slight and variable to warrant this separation. It only differs from typical M. denticulata in the angularity of the lateral lobes, which are not subdivided to so great an extent. The ultimate divisions of these lobes are also more rounded, but this feature is a very variable one. 108 BRITISH DESMIDIACE.E. Var. angusto-sinuata Gay. (PI. L, fig. 5.) M. denticulata var. angusto-sinuata Gay, Monogr. loc. Conj. 1884, p. 52, t. 1, f. -i; West, Alg. Eng. Lake Distr. 1892, p. 722. Cells more angular than in the type, with all the incisions closed and very narrow ; subdivisions of lateral lobes variable, generally retuse and rounded. Length 260 //, : breadth 186 ft; breadth of isthmus 30 jit. ENGLAND. — Loughrigg, Westmoreland ! SCOTLAND. — New Galloway, Kirkcudbright ! Geogr. Distribution. — France. This variety should perhaps be placed as a synonym of var. angulosa. It includes those angular forms in which the incisions are closed and linear. It is no doubt much more generally distributed than is indicated by the localities, but has been overlooked. Var. notata Xordst. (PI. L, fig. 6.) M. denticulata var. notata Nordst. in Bot. Notiser, 1887, p. 155 ; Freslrw. Alg. N. Zeal. 1888, p. 29, t. 2, f. 13 ; Roy and Biss. Scott. Desm. 1893, p. 174; West & G. S. West, Alga-fl. Yorks. 1900, p. 67. Polar lobe with a pair of small teeth on each side of the median notch ; semicells from the vertical view with slightly-undulate margins and with a prominent, somewhat acute papilla at the middle on each side. Length 232-282 ^; breadth 200-220 //,; thickness ENGLAND. — Terrington, X. Yorks ! SCOTLAND.- -Not uncommon (Roy fy Bissett). Suther- land ! Geogr. Distribution. — Germany. Sweden. Finland. New Zealand. This variety may also have a much wider distribution than is here indicated. Var. subnotata West. (PI. L, fig. 7.) M. denticulata var. sultnotata West, Alg. Eng. Lake Distr. 1892, p. 722, t. 9, f . 5. Polar lobe with a small tooth on each side of the MICE AST ERIAS. 109 median notch; semicells in vertical view lanceolate- fusiform, with acuminate poles, and a broad, rounded- conical elevation at the middle on each side. Breadth 170 /A; thickness 50 /x. ENGLAND. — Bowness, Westmoreland ! Note. — In Cooke's f British Desmids' 011 PL XLYII is figured (fig. 5) " M. denticidata var. licmoides Wills," but no descrip- tion of this form is given. It has both polar lobe and lateral lobes much reduced, and appears to us to be merely a mon- strosity produced by rapid cell-division. Imperfectly de- veloped semicells lobed in the manner of "var. licmoides" are not uncommonly met with in collections containing large numbers of M. denticidata. M. denticidata var. intermedia Bennett (( Freshw. Alg. Hamps. and Devon/ 1890, p. 6, t. 1, f. 8) is a doubtful form, so imperfectly described and badly figured that it is quite impossible to identify it. There is, moreover, a var. inter- media of this species described by Nordstedt (in "\Yittr. & Nordst. ' Alg. Exsic/ 1880, no. 370). 13. Micrasterias verrucosa Bissett. (PL LI, fig. 2.) Micrasterias verrucosa "'Roy" in Wolle, Bull. Torr. Bot. Club, 1885, p. 127, t. 51, f. 10; Wolle, Freshw. Alg. U.S. 1887, p. 41, t, 59, f. 10; Bissett in Eoy and Biss. Scott. Desni. 1893, p. 174, t. 1, f. 2 ["Bissett" stated to be the .author of the species]. Cells large, about ly times longer than broad, octangularly elliptic, very deeply constricted, sinus narrowly linear ; semicells 5 -lobed, incisions narrowly linear; lateral lobes somewhat unequal and broadly cuneate, upper ones slightly broader than lower ones ; lobulation similar to that of M. denticidata, ultimate divisions more rounded in the upper lateral lobes than in the lower ones ; polar lobe similar to that of M. denticidata. Vertical view linear - oblong, with acute poles and deeply undulate sides. Cell- wall of a brownish colour, with numerous small subgranulate protuberances scattered over its surface ; the three largest in a transverse row near the median base of 110 BRITISH DESMIDIACEJ:. the semicells are minutely lobecl (or granulated) ; with about four smaller and somewhat indistinct protuber- ances completing the transverse row across the base of the semicell; four smaller protuberances are also subradiately disposed on the polar lobe, five on each of the upper lateral lobes, and two on each of the lower lateral lobes, but the number of these protu- berances is subject to variation. Zygospore unknown. Length 210 /x; breadth ISO jit; breadth of isthmus 29 p,. SCOTLAND. - -Collieston, Bennachie, Powlair in Birse, Slewdrum, Aboyne, Birsemore Loch, Moss of Logie, Morven, and Dalbagie, Aberdeen ; Craithes near Ker- loch, Kincardine (Roy $ Bissett). Loch Ness, Inver- ness ! (./. Murray). Geogr. Distribution. — United States. We have not seen this species, but Mr. James Murray submitted a drawing for our inspection of a specimen of Micrasterias from Loch Ness which could certainly be referred to M. verrucosa. Roy and Bissett state that "it is not granulated in the ordinary sense ; the prominences seem flattened, and their margins cut into rounded segments, similar to the stigma of a species of Poppy, only more deeply cut." 14. Micrasterias Thomasiana Arch. (PL LI, figs. 3-6.) Micrasterias Thomasiana Arch. Description of a new Species of Micras- terias, etc., Proc. Dubl. Nat. Hist. Soc. 1862, p. 72, t. 2, f. 1-5 ; Journ. Micr. Soc., new ser., II, 1862, p. 239, t. 12, f . 1-5 ; Rabenh. Flor. Europ. Alg. Ill, 1868, p. 192 ; Joslma in Journ. Bot. 1882, p. 301 ; Cooke, Brit. Desm. 1886, p. 58, t. 25, f . 1 (in part) ; West, Alg. W. Ireland, 1892, p. 134 ; Alg. Eng. Lake District, 1892, p. 722 ; Roy & Biss. Scott. Desm. 1893, p. 174 ; Nordst. Index Desm. 1896, p. 254 ; West & G. S. West, Desm. Singapore, 1897, p. 163; Alg. S. England, 1897, p. 484; G. S. West, Variation Desm. 1899, p. 384, t. 9, f. 6-8 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 67 ; Alg. N. Ireland, 1902, p. 30. IH. denticulata Breb. forma Thomasiana Jacobs. Desm. Danem. 1875, p. 187. Helierella Thomasiana Kuntze, Eevis. gen. plant. 1891, p. 899. Cells rather large, suborbicnlar, very deeply con- stricted, sinus narrowly linear ; semicells 5-lobed, MICEASTERIAS. Ill incisions between the lobes very narrow and linear; polar lobe narrowly cnneate with concave sides, not projecting, apical margin generally slightly retuse, with a fairly deep median notch, angles on each side of median notch apiculate, outer angles commonly emarginate (sometimes only apiculate) ; lateral lobes fairly equal and broadly cuneate, with a deep and linear primary incision dividing each lobe into two equal lobules, each lobule with a secondary incision (not very deep) and generally with two tertiary in- cisions, four ultimate divisions of each lobule emar- ginate or bidentate (sometimes the tertiary divisions are absent so that each lobule is only subdivided into two parts, which are then tridentate or quadrideiitate) ; with three projections across the base of the semicells, the middle one conical and rounded or apiculate, the lateral ones attenuated and elongate, curved outwrds, and emarginate or bidentate at their apices ; with a conical tooth within the base of each lateral lobe and one within the base of each lateral lobule, also with two, one above the other, within the lower half of the polar lobe, all these teeth being directed outwards. Side view of seniicell narrowly pyramidate, with a rounded basal inflation on each side, apex truncate, lateral margins each with two outwardly-directed, acute projections. Vertical view fusiform, poles acute, with three projections on each side towards the middle, the median projection conical and obtuse or apiculate, the lateral projections very much curved towards the poles and generally bidentate, lateral margins towards the poles serrate. Cell -wall smooth or delicately punctate. Zygospore globose, furnished with stout, furcate spines. Length 174-202 p,; breadth 136-180 /*; breadth of isthmus 21-23 /x; thickness without projections 34-39 /A, with projections 53-57 /x. EXGLAXD. — Angle Tarn, Cumberland ! Bowness, Westmoreland ! (Bissetf). Malham Tarn Bog, \Y. 112 BRITISH DESHIDIACE.E. Yorks ! Pilmoor and Terrington, X. Yorks ! Near Cockley Beck, Lancashire ! Chobham and Thursley Commons, Surrey ! SCOTLAND. — Ross, Aberdeen, Kincardine, Forfar, Perth!, Stirling, Dumbarton (Roy fy Bissett). Suther- land ! Balallan, Lewis, Outer Hebrides ! Zygospore from Fyvie, Aberdeen (Joshua). IRELAND. — Louerh. Akibbon, Donegal ! Glen Caraerh O <— ) o and Cloonee Lough, Kerry ! Dublin and Wicklow (Archer). Geogr. Distribution. — France. Galicia in Austria. Norway. Sweden. Ceylon. Singapore. Java(var.). United States. This species, which in its type form is so characteristic,, is one of the most variable in the genus. The relative size of the basal projections, and the number and disposition of the surface-teeth are very variable, and it is sometimes difficult to obtain two individuals which agree in these respects. M. Thomasiana has a greater affinity with M. denticulata than with M. rotata, and some authors have placed it as a form of that species. It is smaller than M. denticulata, the tabulation is more acute, and it differs in a striking manner in the projections present at the base of the semicells, as well as in the teeth within the bases of the lobes and lobules. It must be borne in mind, however, that these characters are not constant. The teeth within the lobules are generally reduced in number and somewhat irregular in their disposi- tion, and it is not unusual for the median basal projection to be entirely absent. Such forms are figured in Gr. S. West, ' Variation Desm.J 1899, t. 9, figs. 6 and 7. Individuals are frequently met with in which the basal projections are much reduced, and the surf ace -teeth are scarcely evident. These constitute an intermediate series of forms between M. denticulata and M. Thomasiana. Such a form is figured on PL LI, fig. 7. Forma major "West. M. Thomasiana forma major West, Alg. W. Ireland, 1892, p. 134. Cells about half as large again as the type. Length 315 ^u; breadth 285 /n ; breadth of isthmus 38 /u. IRELAND. — Arclerry Lough, G-alway ! MICRASTERIAS. 113 Large specimens (over 300 ju in. length) were frequent in the above-mentioned lake. The largest form we have seen from the United States measured: — length 271 jii; breadth 230 ^u; breadth of isthmus 28 /u. 15. Micrasterias radiata Hass. (Plate LII, figs. 1-9.) Micrasterias melitensis Ralfs in Ann. Mag. Nat. Hist. 1844, xiv, p. 260 t. 6, f. 2. [Not M . melitensis Menegh. 1S4 •/ very slight constriction. * Cells subcylindrical. *t f Lateral margins subparallel. 115. C. Thwaitesit. 116. C. Cucurbita. 11 7. C. Palangula. 118. C. 8ubpalangula. 119. C. par v ulum. 120. C. goniodes. ft Lateral margins not parallel, generally convex. 121. C. viride. 122. C. oblongum. 123. C. Hibernicum. 124. C. turgidum. 125. C. snbturgidum. Cells fusiform-cylindrical. 126. C. aitenuatum. 133 1. Cosmarium obsoletum (Hantzscli) Reinsch. PL LVI, figs. 1-3. Arthrodesmus obsoletus Hantzscli in Kabenh. Alg. 1862, no. 1407 ; Grun. Diat. \i. Desm. Ins. Bank. 1865, p. 15, t. 2, f. 28. Cosmarium obsoletum (Hantzscli) Keinsch, Spec. Gen. Alg. 1867, p. 1-42, t. 22, D. I, f. 1-4; Lund. Desm. Snec. 1871, p. 38 ; Nordst. Alg. et Char. I, 1880, p. 7, t. 1, f. 9 ; Wille, Sydamerik. Algfl. 1884, p. 16, t. 1, f. 33 ; De Toiii, Syll. Alo-. 1889, p. 974; West, Alg. W. Ireland, 1892, p. 144 ; Alg. Eng. Lake Distr. 1892, p. 724 ; Liitkenmll Desm. Attersees, 1893, p. 556 ; Nordst. Index Desm. 1896, p. 186 ; West & Of. S. West, Desm. Sino-apore, 1897, p. 164 ; Freshw. Chlorophy. Koli Chang,,1901, p. 87 ; Freshw. Alg-. Ceylon, 1902, p. 164. Didymidium (Cosmarium) obsoletum Reinsch. Algenfl. Frank. 1867, p. 110, t, 9, f. 5. UrsineUa obsoleta Ktintze, Eevis. gen. plant. 1891, p. 925. Cosmarium palustre Turn. Freshw. Alg. E. India, 1893, p. 60, t. 8, f. 65, t. 9, f . 29. C. palustre var. ovale Turn, 1. c. t. 9, f. 1. Cells of medium size, transversely elliptic, a little broader tliaii long, deeply constricted, sinus narrowly linear with a dilated apex ; semicells semi-elliptic (depressed-semicircular), basal angles submamillate and slightly thickened, apex generally slightly flat- tened. Side view of semicell depressed-globose. Vertical view elliptic, with obtusely conical poles, ratio of axes 1 : 2*1. Cell -wall punctulate (or finely scrobicu- late), sometimes slightly thickened in the centre of the semicells. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 34-46 ^ ; breadth 42-54 p. ; breadth of isth- mus 15'5-20/x; thickness 20-24 /x. ENGLAND.- -Bowness, Westmoreland ! \YALES. — Yr Orsedd, Carnarvonshire ! IRELAND.- -Clogerheen, Kerry ! Geogr. Distribution.- -Germany. Austria and Gralicia. Sweden. N. Russia. Poland (var.). Central China. Japan. India. Ceylon. Siam. Singapore. Java. Egypt. New Zealand (var.). Australia. United States. Brazil. This species is much more abundant in tropical and sub- tropical countries than in temperate climates, and it exhibits 134 BRITISH DESMIDIACE^l. a considerable range of variation. There is a thickening of the cell-wall at the basal angles of the seniicells which com- monly gives them a submamillate appearance. Some of the tropical forms attain a large size : — length 57 -64 n ; breadth 67-75 JJL ; breadth of isthmus 30-35 JJL ; thick- ness 36 /u. In these specimens the thickening of the basal angles is generally prominent,, and passing through it is a large conical pore, the wider end of which is towards the interior of the cell-wall. We give a figure of one of these specimens from Singapore to show this character (PI. LVI, fig. 4). Sometimes the mamillate thickening becomes quite hyaline with the exception of the conical pore, which then stands out very prominently, and has the appearance of a short spine attached to the basal angle. Turner figured this pore as a spine at the angle, and he put forward the name i{ Cosmarium palustre '' for typical specimens of the large form of C. obsoletum which is so abundant in tropical Asia. It is in old individuals in which the cell-wall becomes of a yellow or yellow-brown colour that this " spinate " appearance is most marked. Sometimes the actual thickening of the basal angle has the form of a bluntly-conical mucro. The large tropical forms have recently been named " var. Sitvense'1 by Gutwiiiski (' Alg. Ins. Java/ 1902, p. 594, t. 38, f. 39), and so far as is known they are characteristic of the Lido-Malay region. The British specimens are usually of small size and they show 110 trace of the pore which is present in the basal angles of the large tropical forms. The cell-wall of the smaller forms is finely punctate, but that of the larger forms is some- what sparsely and finely scrobiculate. 2. Cosmarium Smolandicum Lund. (PL LVI, fig. 5.) Cosmarium Smolandicum Lund. Desna. Suec. 1871, p. 39, t.2, f. 17 ; Wolle, Desm. U.S. 1884, p. 66, t. 16, f. 35, 36 ; De Toni, Syll. Alg. 1889, p. 984 ; Nordst. Index Desm. 1896, p. 235. Ursinella Smolandica Kuntze, Eevis. gen. plant. 1891, p. 925. Cells of medium size, subcircular, a little longer than broad, very deeply constricted, sinus somewhat narrow and linear ; semicells subsemicircular, apices convex but sub truncate in the middle, basal angles obtuse and furnished witli a prominent papilla. Side COSMAEIUM. 135 view of semicell circular. Vertical view elliptic, ratio of axes 1 : 1*71. Cell-wall punctate. Chloroplasts axile, eacli with two pyrenoids. Zygospore unknown. Length 54 p. ; breadth 48 p. ; breadth of isthmus 12 p, ; thickness 28 p.. Geogr. Distribution. — Sweden. United States. The typical form of this species is not known to occur in the British Islands. Var. angustatum nob. (PI. LVI, figs. 6, 7.) C. obsoletum (Hantzsch) Eeinsch var. angustatum West, Alg. W. Ireland, 1892, p. 144, t. 24, f. 22. C. obsoletiim var. angustatum West forma galiciensis Gutw. Norm. Alg. Nov. 1896, p. 49, t. 7, f. 46. A variety with the sinus closed and linear, with the basal angles of the semicells rectangular and the lower part of the sides straight and parallel, and with the apex in the middle subtruncate. Length 42 '5-43 '5 //,; breadth 34-37 p. ; breadth of isthmus 11-14 p.. IRELAND. — Carrantuohill, Kerry ! Geogr. Distribution. — Gralicia in Austria. The Desmid described as Cosmarium obsoletum var. angus- tatum is much better referred to C. Smolandicum Lund. We have examined further specimens from Carrantuohill and find that the figure given in the ' Alg. W. Ireland/ tab. 24, fig. 22, is not a good one. The basal angles of the semicells are rectangular, and the ruucro at each angle, although less pro- minent than in the type, projects laterally. The upper angles are also more rounded and the apex is more distinctly truncate. Thus, the specimen found by Grutwinski in Austria, which he named ' C. obsoletum var. angustatum forma galiciensis,' and about which he remarks : " a forma irlandica diff ert angulis basalibus alias protractis, angulis superioribus magis rotundatis vel oblique truncatis," must also be referred to C. Smolandicum var. angustatum. Gutwinski's measurements of his Austrian specimens (length 40-43 fj. ; breadth 30'4-35 /j. ; breadth of isthmus 11-13 ju) agree almost exactly with the dimensions of the Irish forms. 136 BRITISH DESMIDIACEJ2. 3. Cosmarium taxichondriforme Eiclil. & Gutw. (PI. LVI, figs. 8-10.) Cosmarium taxichondriforme Eiclil. & Gutw. Nonn. Spec. Alg. Nov. 1894, p. 169, t. 4, f. 23 ; Nordst. Index Desm. 1896, p. 250. Cells rather small, as long as broad, circular-hexa- gonal, deeply constricted, sinus narrow and slightly open ; semicells pyramidate-semicircular, basal angles very faintly produced and slightly thickened, generally turned downwards. Side view of semicell subcircular, with flattened apices. Vertical view elliptic with pro- duced poles, ratio of axes 1:2. Cell- wall finely punctate. Chloroplasts axile, each with one pyrenoid. Zygospore unknown. Length 31-41-5 p.; breadth 31-47 ft; breadth of isthmus 10-15 /x,; thickness 17-22 p. ENGLAND.- -Bowness, Westmoreland ! Geogr. Distribution. — Gralicia in Austria. In outward appearance this species bears considerable re- semblance to Cosmarium taxiclwndrum Lund.,, but is easily distinguished by the entire absence of surface granules and by the presence of only one pyrenoid in the axile chloroplasts. It still more closely resembles a tropical species, C. nudum (Turn.) Gutw. (= C. taxiclwndrum var. nudum Turn.), from which it is distinguished by the single pyrenoid in each semi- cell and by the attenuation of the poles of the vertical view. It should also be compared with C. crassangulatum Borge (' Siissw. Chlor. Archang/ 1894, p. 25, t. 2, f. 23). We have only observed this species from some small water- lily pools near Bowness in the English Lake District. 4. Cosmarium circulare Keinsch. (PL LVI, figs. 11, 13, 14.) Cosmarium circulare Keinscb, Spec. Gen. Alg. 1867, p. 113, t. 22, C. I, f. 1 -4 ; Lund. Desm. Suec. 1871, p. 41 ; Wolle, Freshw. Alg. U.S. 1887, p. 28, t. 57, f. 37 ; Hansg. Prodr. Algenfl. B5hm. 1888, p. 249 ; De Toni, Syll. Alg. 1889, p. 975 ; West, Alg. N. Yorks. 1889, p. 292 ; Alg. N. Wales, 1890, p. 288; Alg. W. Ireland, 1892, p. 144; Nordst, Index Desm. 1896, p. 73. Didymidium (Cosmarium) circulare Keinsch, Algenfl. Frank. 1867, p. 108, t. 10, f. 2. Ursinella circularis Kuntze, Keris. gen. plant. 1891, p. 924. COSMAK1UM. 137 Cells large, circular, about as long as broad, deeply constricted, sinus very narrow and linear, dilated at the extremity ; semicells semicircular with rounded basal angles. Side view of semicell rounded-ovate or subcircular. Vertical view narrowly elliptic, ratio of axes 1:2-6. Cell-wall punctulate. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 54-95 /A; breadth 54-90 ^; breadth of isthmus 22-28 ^; thickness 25-38/1. ENGLAND. --Mickle Fell, X. Yorks ! "WALES. — Snowdon, Carnarvonshire ! SCOTLAND. — Loch Ruthven, Inverness ; near Loch Mharc, in Athole, Perth (Ron $• Bissett). IRELAND.- -Creggan Lough, Gralway ! (leog-r. Distribution. — Germany. Galicia in Austria. Hungary (var.). Sweden. S. Russia, India. E. Africa. United States. Brazil. C. circulars Reiiisch differs from C. Ralfsii Breb. in the outward form of its cells and in its axile chloroplasts. The semicells of C. circular e are semicircular in outline and never exhibit the pyramidate character which is so conspicuous in C. Ralfsii. C. circulare is distinguished from C. Lundellii Delp. by its semicircular semicells and its elliptical vertical view. The vertical view of C. Lundellii is drawn out at the poles and is sometimes almost rhomboid-elliptic, whereas that of C. circu- lar e is narrowly elliptic. There is also a thickening of the cell-wall in the centre of the semicells of C. Lundellii which is never present in C. circulare. Forma minor nob. (PI. LVI, fig. 12.) Cosmarium circulare Eacib. N"onn. Desm. Polon. 1885, p. 83, t. 11, f. 1. C. Raciborslcianum De Toiii, Syll. Alg. 1889, p. 975. Ursinella Raciborskiana Kuntze, Eevis. gen. plant. 1891, p. 925. Length 33-35 ju; breadth 35 p. ; breadth of isthmus 12-14 p. ; thickness 19 JLC. IRELAND. — Creggan Lough, Galway ! Geogr. Distribution. — Poland. 138 BRITISH DESMIDIACE2E. 5. Cosmarium Lundellii Delp. (PI. LVII, figs. 1, 2). Cosmarium Lundellii Delp. Desm. subalp. 1877, p. 13, t. 7, f . 62-64 ; Wille, Norges Ferskv. Alg. 1880, 1, p. 33 ; Sydamerik. Algfl. 1884, p. 47, t. 3, f. 89 ("forma ") ; De Toni, Syll. Alg. 1889, p. 956 ; Nordst, Index Desm. 1896, p. 160 ; West & G. S. West, Fresliw. Alg. Ceylon, 1902, p. 1£2. Ursinella Lundellii Kuntze, E,evis. gen. plant. 1891, p. 925. Cosmarium subcirculare Turn. Freshw. Alg. E. India, 1893, p. 52, t. 8, f. 3; t. 9, f. 27, 37. Cells large, subcircular, about as long as broad (or a little longer), deeply constricted, sinus linear with a dilated apex ; semicells subsemicircular or pyramidate- semicircular, basal angles broadly rounded. Side view O f of semicell subcircular. Vertical view elliptic, ratio of axes 1 : 1'94, poles slightly drawn out. Cell-wall punctate, generally thickened in the centre of the semicells. Chloroplasts axile, with prominent ridges, and with two laro-e pvrenoids. O It/ Zygospore unknown. Length 79-88 /* ; breadth 69-79 ^ ; breadth of isth- mus 30-41 //, ; thickness 42-45 ILL ENGLAND. — Mousehole Cave, Cornwall ! Geocjr. Distribution. — Germany. Gralicia in Austria. Italy. Norway. Poland. Central China (forma). India. Central and E. Africa. Madagascar. Brazil. Ecuador. Argentina. This species is much more abundant in the tropics than in temperate climates, and quite a number of distinct varieties of it exist. It differs from C. Ralfsii Breb. in its somewhat smaller size, its less deep constriction and consequently broader isthmus,, in the more rounded basal angles of the semicells, and in its axile chloroplasts. The breadth of the isthmus as compared with the breadth of the semicell is as 1 : 4'3 in C. Ralfsii, whereas in C. Lundellii it is only 1 : 2*5. Var. ellipticum West. (PI. LVII, figs. 3, 4.) C. Lundellii var. ellipticum West, New Brit. Fresliw. Alg. 1894, p. 5, t. 1, f. 11. Cells smaller than in the type, about 1-J- times longer than broad, with a narrower isthmus. COSMARIUM. 139 Length 68-73 p. ; breadth 53-55 /x ; breadth of isth- mus 16-21 /A; thickness 26-29 (JL. WALES. — Snowdon, Carnarvonshire (at 3,000 ft.) ! SCOTLAND.- -Ben Laoigh, Perthshire ! Compared with its breadth this variety is proportionately longer than any of the other varieties of C. Lundellii. Var. corruptum (Turn.) West & Gr. S. West, (PI. LVII, figs. 5, 6.) Cosmarium corruptum Turn. Freslrvv. Alg. E. India, 1893, p. 51, t. 8, f. 2. C. subcirculare Turn. var. rugosum Turn. 1. c. p. 52, t. 8, f. 7. C. rotundum Turn. I.e. p. 58, t. 8, f. 48. C. Lundellii Delp. var. corruptum (Turn.) West & G. S. West, Freshw. Alg. Ceylon, 1902, p. 162. ' Cells smaller, sinus often somewhat open towards the exterior ; cell-wall with variable scrobiculations of small size, generally larger and more distinct near the margin ; apex of semicells slightly subtruncate. Length 51-63 ^i; breadth 48*5-61^; breadth of isthmus 23-28*5 /x. ENGLAND. — Bowness, Westmoreland ! Geogr. Distribution. — Gralicia in Austria. India. Ceylon. This variety only differs from typical C. Lundellii in its somewhat smaller size and in the greater distinctness of the scrobiculations near the margins of the semicells. The sinus is generally closed in its median part., although dilated at its extremity and opening considerably towards the exterior. The plants named by Turner Cosmarium corruptum, C. sub- circulare var. rugosum, and C. rotundum, are most certainly forms of one species, and we have thought it best to place them as a variety of C. Lundellii under the name "cor- ruptum." C. Lundellii var. corruptum should be compared with C. galeritum Nordst., from which it can be distinguished by its wider and more depressed semicells,, with less truncate apices, and by its much broader isthmus. 6. Cosmarium pachydermum Lund. (PI. LVII, fig. 7.) Cosmarium pachydermum Lund. Desm. Suec. 1871, p. 39, t. 2, f. 15; Kirchn. Alg. Schles. 1878, p. 149; Wolle, Desm. U.S. 1884, p. 70, t. 15, 140 BRITISH DESMIDIACE.E. f . 2-4 ; Cooke, Brit. Desm. 1886, p. 85, t. 37, f . 1 ; Hansg. Prodr. Algenfl . Bohm. 1888, p. 198; De Toni, Syll. Alg. 1889, p. 970; West, Alg. W. Ireland, 1892, p. 14-i ; Alg. Eng. Lake Distr. 1892, p. 724 ; Roy & Biss. Scott. Desm. 1894, p. 170 ; Nordst. Index Desm. ]896,p. 193; West & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-n. Yorks. 1900, p. 69. C. pachydermum a. typicum Klebs, Desni. Ostprenss. 1879, p. 34, t. 3, f. 36. Ursinella pachyderma Kimtze, Revis. gen. plant. 1891, p. 925. Cells large, broadly elliptic, about 1J times as long as broad, deeply constricted, sinus narrowly linear with a dilated apex ; semicells widely semi-elliptic, apices broad, basal angles broadly rounded, lower part of sides at first somewhat straight. Side view of semicell subcircular. Vertical view elliptic, ratio of axes about 1 : 1'5. Cell- wall thick and densely punc- tate. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 78-117 ^; breadth (50-87 ^', breadth of isthmus 30-40 p,-, thickness 50-59 /x; thickness of cell- wall 2 '5-3 JJL. EXGLAXD.- -Foot of Brant Fell, Westmoreland ! Malham Tarn and Penygheiit, \V. Yorks ! Pilmoor near Thirsk, X. Yorks ! Mitcham Common and near Chapel Wood, Surrey! Millford Lake, Hants (Ron). Xear Bovey Tracey, Devon (Bennett). Tremethick Moor, Cornwall ! SCOTLAND.- -Sutherland, Ross, Aberdeen, Kincardine, Stirling, Argyll (in Mull) (Rot/ $ Bissett). IRELAND. - -Lough Aunierin, G-alway ! Dublin and \Yicklow (Archer). Clough, Antrim ! Geoc/r. Distribution.- -France. Germany. Austria and Gralicia. Hungary. Italy. Xorway. Sweden. Denmark. Bornholm. Finland. N. and S. Russia. Faeroes. Japan. Sumatra. Java. New Zealand. Australia. Azores. United States. Brazil. Argen- tina. Patagonia. C. pachydermum is rendily distinguished from C. Lundetlii by its inflated semicells and its thick cell-wall. The vertical view is also more elliptic. Var. sethiopicum nob. (PI. LVII, figs. 8, 9.) C. Lundellii var. athiopicum West & Ci. S. West, Welw. Afric. Freshw. Alg. 1897, p. 32 ; Scott. Freshw. Plankton, I, 1903, p. 526, 541. COSMARIUM. 141 Cell-wall much thinner than in the type, finely scro- biculate and minutely punctate between the scrobicu- 1 at ions. Length 69-107 p; breadth 61-80 p.; breadth of isthmus 28-33 /x ; thickness 40-44 /x. SCOTLAND.- -Plankton of Loch Shin, Sutherland ! Geogr. Distribution. — T\r. Africa. This variety was at first erroneously referred to C. Lundellii, but the form of the semicells both in the front and vertical view shows clearly that it is a thin- walled variety of C.pachy- dermum. Careful examination of the cell-wall of this variety reveals a large number of minute punctulatioiis scattered between the larger ones. 7. Cosmarium Ralfsii Breb. (PL LVII, fig. 10 ; PI. LVIII, figs. 1, 2.) Cosmarium Ralfsii Breb. in Kalis' Brit. Desni. 1848,, p. 93, t. 15, f . 3 ; Arch, in Pritcli. Infus. 1861, p. 731 ; Kabenh. Flor. Enrop. Alg. 1868, III, p. 161 ; Lund. Desni. Suec. 1871, p. 52 ; Nordst. Xorges Desni. 1873, p. 25 ; Wolle, Desni. U.S. 1884, p. 69, t. 15, f. 1 ; Cooke, Brit. Desni. 1886, p. 85, t. 36, f. 12 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 193; West, Alg. N. Wales, 1890, p. 288; Alg. W. Ireland, 1892, p. 163; Alg. Eng. Lake Distr. 1892, p. 729; Roy & Biss. Scott. Desm. 1894, p. 173 ; Nordst. Index Desm. 1896, p. 220 ; West & G-. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Torks. 1900, p. 68 ; Alg. K". Ireland, 1902, p. 33. Didymidium (Cosmarium) Ralfsii Eeinscli, Algenfl. Frank. 1867, p. 108. Cosmarium Ralfsii a. typicum Klebs, Desm. Ostpreuss. 1879, p. 33, t. 3, f. 33-35, 37 ;'Eacib. Norm. Desni. Polon. 1885, p. 70. Cosmaridium Ralfsii Hansg. Prodr. Algenfl. Bohm. 1888, p. 246. Pleurotseniopsis (Cosmaridium} Ralfsii (Breb.) De Toni, Syll. Alg. 1889, p. 911. Cells large, subcircular, a little longer than broad, very deeply constricted, sinus narrowly linear with a dilated apex ; semicells subpyramidate-semicircular, basal angles rounded, sides slightly convex, apex broadly rounded or truncately rounded. Side view of semicell subcircular. Vertical view rhomboid-elliptic, ratio of axes about 1 : 1*9. Cell- wall finely punctate or even scrobiculate, sometimes almost smooth. Chloro- plasts parietal, consisting of several irregular bands 142 EEITISH DESMIDIACE^l. running from base to apex of each semicell, each band with several rather small pyrenoids. Zygospore unknown. Length 11 2-120 ft; breadth 95-104 /A; breadth of isthmus 21-25 p.; thickness 50 //,. ENGLAND. — Cumberland! Westmoreland! (Bissett). W. and IN". Yorks ! Lancashire! Norfolk (CooJce). Warwick (Wills). Surrey! Sussex (Ralfs). Kent (Ralfs). Hants! (Rolfs). Devon I (Bennett). WALES. — General in Carnarvonshire (up to 2,700ft. on Grlyder Fawr) ! Dolgelly and Ffestiniog, Merioneth ! Llyn Coron, Anglesey ! SCOTLAND.- -Sutherland ! , Ross, Inverness ! , Aber- deen, Kincardine, Forfar, Perth ! , Argyll, Arran (Roy fy Bissett). Outer Hebrides ! Orkneys ! IRELAND.- -Widely distributed in Donegal, Galway, and Kerry ! Mayo ! Dublin and Wicklow (Archer). Geogr. Distribution.- -France. Belgium. Germany. Galicia in Austria. Hungary. Norway. Sweden. KT. Russia. Poland. Azores (var.). United States. This characteristic species is widely distributed in the upland districts of the British Islands, and often occurs in abundance among submerged Sphagnum. It is frequently associated with Cosmarium Cucurbita, Euastrum insigne, Micrasterias oscitans var. mucronata, M. truncata, Gymnozyga moniliformis, Tetmemorus granulates, and Netrium Digitus. It is characterized by its pyramidate-semicircular semicells with a rounded apex, by its deep constriction, and by the parietal chloroplasts. The cell-wall is generally finely punc- tate, hut may be delicately scrobiculate, and old individuals often become quite asperulate on the exterior. Wolle gives a minimum length of 70 /UL and a minimum breadth of 60 fj. for his American specimens, but we have not seen any British forms so small as this. Var. montanum Racib. (PI. LVIII, fig. 3.) Cosmarium Ralfsii var. montanum Racib. Norm. Desin. Polon. 1885, p. 70, t, 10, f. 4 ; West, Alg. W. Ireland, 1892, p. 163. Pleurotseniopsis Ralfsii var. montana (Racib.) De Toni, Syll. Alg. 1889, p. 911. Cells with the sinus opening outwards, basal angles of semicells less rounded and slightly produced. COSMARIUM. 143 Length 87-1 '28 /x, ; breadth 76-101 /x: breadth of isthmus 20-23 //,. IRELAND. — Carrantuohill, Kerry ! t/ Geoyr. Distribution. — Gralicia in Austria. Poland. 8. Cosmarium perforatum Lund. (PL LVIII, figs. 4, 5.) Cosmarium perforatum Lund. Desin. Suec. 1871, p. 40, t. 2, f. 16; Wolle, Freshw. Al?. U.S. 1887, p. 28, t. 57, f . 32 ; De Toni, Syll. Alg. 1889, p. 977 ; West, Alg. W. Ireland, 1892, p. 144 ; Alg. Eng. Lake Distr. 1892, p. 724 : Liitkem. Desm. Attersees, 1893, p. 556 ; Eoy & Biss. Scott. Desni. 1894, p. 171; Nordst. Index Desin. 1896, p. 199; West & G. S. West, Alg. N. Ireland, 1902, p. 33. Ursinella perforata Kuntze, Revis. gen. plant. 1891, p. 925. Cosmarium perforatum a. typicum Gutw. Flor. Glon. Okolic Lwo\va, 1891, p. 48. Cells of medium size, angular-subcircular, a little longer than broad, moderately constricted, sinus some- what open, widening outwards from an acute apex ; semicells subpyramidate-semicircular, basal angles rounded-truncate, sides almost straight for a short distance, then converging to the subtruncate or sub- retuse apex. Side view of semicell subcircular, broad at the base and slightly retuse at the apex. Vertical view elliptic with pointed poles, ratio of axes about 1 : 1*56. Cell- wall rather thick, punctate, with a sub- triano'ular area in the centre of the semicells near the o isthmus furnished with about 20 small scrobiculations. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 60-75/0,; breadth 5 7-63 ^; breadth of isthmus 26-36 JJL : thickness 38-40 /x. ENGLAND. — Bowness, Westmoreland ! SCOTLAND.- -Loch Ruthven, Inverness ; Dalbagie and Loch Ullachie near Ballater, near Castleton, and Birse- more, Aberdeen (Roy $ Bissett}. Dumfries ! IRELAND. — Loughs Akibbon, Grartan, and Sproule, Donegal! Ballynahinch, Lough Derryclare, Lakes E. of Lough Bonn, and small lakes Clifden to Round- stone, G-alway ! 144 BRITISH DESMIDIACEJE. Geogr. Distribution. — France. Germany. Austria and Galicia. Norway. Sweden. Bornliolm. X. and S. Russia. Faeroes. Greenland. United States. The species is well characterized by the outward form of the semicells, the open sinus and broad isthmus, as well as by the large, scattered scrobiculations in the centre of the semi- cells. 9. Cosmarium ocellatum Eichler & Gutw. (PL LVIII, fig. 6.) Cosmarium ocellatum Eiclil. & Gutw. Norm. Spec. Alg. Nov., 1894, p. 164, t. 4, f. 7. Cells small, 1-g— 1J times as long as broad, deeply constricted, sinus linear and dilated towards the apex ; semicells subsemicirciilar-pyramidate, basal angles and apex rounded. Side view of semicell subcircular. Vertical view elliptic, ratio of axes about 1 : 2*25. Cell-wall smooth or very finely punctate, with a large scrobiculation in the centre of the semicells. Chloro- plasts axile, each with one pyrenoid. Zygospore unknown. Length 20-30 /x; breadth 17-23^; breadth of isthmus 4-6 ^ ; thickness 9-14 //,. Geogr. Distribution.- -Q&licia in Austria. The typical form of this species has not yet been observed in the British Islands. Yar. incrassatum West & G. S. West. (PL LVIII, fig. 7.). C. ocellatum var. incrassatum West & G. S. West, Alg. S. England, 1897, p. 485, t. 6, f. 12. A variety with the sinus always open ; semicells with subtruncate apices. Cell-wall in the centre of the semicells with a thickened area of a yellowish colour, containing a small central scrobiculation surrounded by 2-5 smaller ones. Vertical view elliptic, with a slight, flattened protuberance at the middle on each side. COSMARIIDI. 145 Length 28-30 p. ; breadth 24-26 p ; breadth of isthmus 5'5-6'5/x; thickness 14'5— 15 p. ENGLAND.- -Thursley Common, Surrey ! New Forest, Hants ! This variety was abundant amonsr Utricularia minor in both t/ c3 the above-mentioned localities. 10. Cosmarium cyclicum Lund. (PI. LVIII, figs. 8, 9.) Cosmarium cyclicum Lund. Desm. Suec. 1871, p. 35, t. 3, f. 6 ; Cooke, Brit. Desm. 1886, p. 116, t. 40, f. 1J ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 196 ; De Toni, Syll. Alg. 1889, p. 983 ; West, Alg. N. Yorks. 1889, p. 293 ; Alg. N. Wales, 1890, p. 290 ; Alg. Eng. Lake Distr. 1892, p. 728 ; Nordst. Index Desm. 1896, p. 9-i : West & G. S. West, Alga-fl. Yorks. 1900, p. 69. C. Turnerianum Mask. Further Notes N. Zeal. Desm. 1889, p. 18, t. 3, f. 28. Ursinella cyclica K/imtze, Eevis. gen. plant. 1891, p. 924. Cells of medium size, circular or transversely circular- elliptic, about as long as broad, deeply constricted, sinus very narrow with a dilated apex ; seinicells semi- circular, angles slightly rounded or obliquely truncate, marerin regularly crenate with about 12 crena?. and O O e/ with two or three parallel rows of small undulations within the margin. Side view of semicell obcuneate, apex rounded-truncate. Vertical view narrowly fusi- form-elliptic, undulate towards the poles, ratio of axes about 1 : 2*2. Cell-wall smooth. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 49-52 ju; breadth 52-58 /A; breadth of isthmus 17-27*5 ^ ; thickness 25-26 ^. ENGLAND. — Borrowdale, Cumberland ! Near Bow- ness (Bissett), and Helvellyn ! , Westmoreland ! Mickle Fell, N. Yorks ! WALES.- -Capel Curig (Cooke fy Wills), Snowdon!, Llyn Idwal ! , T Foel Eras ! , and Llyn-an-af on ! , Car- narvonshire. IRELAND. — Dublin and Wicklow (Archer'). Geogr. Distribution. — France. Germany. Austria VOL. II. 10 146 BRITISH DESMIDIACE^. and Bohemia (var.). Italy. Norway. Sweden. Greenland. Spitzbergen. Nova Zembla. United States. C. cyclicum Lund, differs from C. undulatum Corda in its more depressed semicells with less rounded basal angles, and in the possession of two pyrenoids in each chloroplast. Var. arcticum Nordst. (PL LVIII, fig. 10.) C. cyclicum Lund, subsp. arcticum Nordst. Desm. Spetsb. 1872, p. 31, t. 6, f . 13 ; Desm. Ital. 1876, p. 37 ; Boldt, Desm. Gronl. 1888, p. 22 ; De Toni, Syll. Alg. 1889, p. 983 ; Eoy & Biss. Scott. Desm. 1894, p. 44 ; Borg. Fresliw. Alg. Ostgronl. 1894, p. 15. C. cyclicum Lund. var. maculatum Sclimidle, Weit. Beitr. Algenfl. Rheineb. 11. Schwarzwald. 1895, p. 76, t. 1, f. 7. Cells subcircular, inclined to be somewhat sexanoai- ' o lar ; semicells with the crena3 of the margin and within the margin bigranulate (as if emarginate), those towards the base unigranulate, apex 4-crenate and without granules. Length 57'5-75jn; breadth 65-75 /x; breadth of isthmus 22-28 p ; thickness 33-37 p. SCOTLAND.- -Aberdeen, Kincardine, Forfar, and Ren- frew (Roy fy Bissett). Geogr. Distribution. — G-alicia and Bohemia in Austria. Italy. Norway. Bornholm. Poland. Faeroes. Greenland. Spitzbergen. Nova Zembla. The figure of this variety given by Roy and Bissett is not like that of Nordstedt's, hnt it suggests var. arcticum in the minute binate granules. We give a copy of Roy & Bissett's figure (PI. LVIII, fig. 11), and we think it stands near to var. Nordstedtianum, as the granules are not evident at the margin. The form described by Schmidle as " var. maculatum ' is intermediate in character between the figure given by Nord- stedt and that given by Roy & Bissett. Var. Nordstedtianum (Reinsch) nob. (PI. LVIII, fig. 12.) Cosmarium Nordstedtianum Reinsch, Contrib. Alg. et Fungi, 1875, p. 89, t. 10, f. 11. C. cyclicum Lund. var. angulatum West, Alg. N. Yorks. 1889, p. 293, t. 291, f. 2; Alg. Eng. Lake Distr. 1892, p. 728; West & G. S. West, Alga-fl. Yorks. 1900, p. 69. COSMARIUM. 147 Ursinella Nordstedtiana Kxiiitze, Revis. gen. plant. 1891, p. 925. C. cyclicum Lund. var. truncatum Borge, Siissw. Chlor. Archang. 1894, p. 21 ; [vide West in Jourii. Bot. 1895, p. 67.] Cells distinctly hexagonal, usually a little broader than long ; apices truncate or subtruncate, less crenate than the lateral margins. Length 48-50 p, ; breadth 54-66 JJL ; breadth of isth- mus 19-21 p. ; thickness 20-23 /*,. ENGLAND.- -Borrowdale, Cumberland ! Penyghent, W. Yorks! Mickle Fell, X. Yorks ! Wimbledon Common, Surrey. IRELAND.- -Fintowii, Donegal ! Geogr. Distribution. — Gralicia in Austria. N. Russia. We have observed this variety in greater abundance than typical C. cyclicum. It is well characterized by its hexagonal cells with truncate apices. 11. Cosmarium fontigenum Nordst. (PI. LIX, figs. 16, 17.) Cosmarium fontigenum Nordst. in Wittr. & Nordst. Alg. Exsic. 1878. 110. 171 ; and in fasc. 21 (1889), p. 43 cum fig. xylogr. ; De Toni, Syll. Alg. 1889, p. 1010 ; Roy & Biss. Scott. Desm. 1894, p. 101 ; West & G-. S. West, Alg. S. England, 1897, p. 486. Ursinella fontigena Knntze, Revis. gen. plant. 1891, p. 924. Cells small, about as long as broad, deeply con- stricted, sinus very narrow with a slightly dilated extremity; semicells broadly subpyramidate, apex broadly truncate, basal angles rounded, sides slightly convex or almost straight, upper part of lateral margins slioiitly crenate. Side view of semicell subcircular. O t) Vertical view narrowly elliptic, with a small protuber- ance at the middle on each side. Cell-w^all finely punctate. Chloroplasts axile, each with one pyrenoid. Zy go spore unknown. Length 20-26 JLI; breadth 20-25 /* ; breadth of isth- mus 6-8 /x; thickness 11-1 3 /A; breadth of apices about 8-11 p.. ENGLAND.- -Puttenham Common, Surrey ! SCOTLAND.- -Ross; Skye and near Brin, Inverness; Aberdeen; Kincardine; Perth (Roy fy Bissett). 148 BRITISH DESMIDIACE^E. IRELAND. — Dublin and Wicklow (Archer). Geogr. Distribution. — Germany (forma). Norway. Sweden. Bornholm. G-utwinski lias described a Desmid from Galicia which he named C. pseudofontigenum (vide Griitw. ' Walir. d. Prioritat/ 1890, p. 67; fFlor. Glon. Okolic Lwowa/ 1891, p. 40, t, i, f. 11), but we do not see how it can be specifically separated from C. fontigenum Nordst. as it only differs in the reduction of the small central protuberance. In dimensions and in all other characters it agrees well with C. fontigenum and there- fore it can only be considered as a form of it. 12. Cosmarium undulatum Corda. (PI. LIX, figs. 1-3, 5.) Cosmarium undulatum Corda in Aim. cle Carlsbad, ] 839, p. 243, t. 5, f . 26 ; Ralfs, Brit. Desni. 1848, p. 97, t. 15, f. 8 ; Arch, in Pritch. Infus. 1861, p. 732, t. 2, f. 33, 34 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 165 ; Lund. Desm. Siiec. 1871, p. 35 ; Kirchn. Alg. Scliles. 1878, p. 149 ; Wolle, Desm. U. S. 1884, p. 67, t. 16, f. 20, 21 ; Cooke, Brit. Desni. 1886, p. 97, t. 37, f . 16 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 196 ; West, Alg. N. Wales, 1890, p. 289 ; Alg. W. Ireland, 1892, p. 151 ; Alg. Eng. Lake Distr. 1892, p. 726; Eoy & Biss. Scott. Desm. 1894, p. 177; Nordst. Index Desm. 1896, p. 265 ; West & G. S. West, Alg. S. England, 1897, p. 488 ; Alga-fl. Yorks. 1900, p. 73. Diclymidium (Cosmarium) undulatum Reinsch, Algenfl. Frank. 1867, p. 117 (in part). Euastrum (Cosmarium) undulatum Gay, Monogr. loc. Conj. 1884, p. 60. Ursinella undulata Knntze, Eevis. gen. plant. 1891, p. 925. Cells rather small, quadrate-elliptic, about 1-^-1-J times as long as broad, deeply constricted, sinus narrow with a dilated extremity ; semicells widening upwards near the base, then subsemicircular, margins with 10 to 12 equal undulations. Side view of semicell sub- circular. Vertical view elliptic, ratio of axes 1 : I'oo. Cell-wall smooth. Chloroplasts axile, each with one pyrenoid. Zygospore unknown. Length 54-64 ^ ; breadth 39-52 p ; breadth of isth- mus 12-5-17 /x: thickness 27'5-30 //,. ENGLAND.- -Westmoreland ! (Ralfs). W., N., and E. Yorks! Cheshire (Eoy). Warwick (Wills). Glou- cester (Ralfs). Surrey! Sussex (Ralfs). Cornwall! (Marquand). cosMARimr. 149 WALES.- -Bethesda!, Glyder Fawr and Pen-y-gwryd (Roy), Capel Curig ! (Coolie $' Wills), Carnarvonshire. Dolgelly, Merioneth (Rnlfs). Llyn Coron, Anglesey! SCOTLAND.- -Ross, Inverness !, Banff, Aberdeen, Kin- cardine, Forfar, Perth!, Argyll (Roy $ Bissett). IRELAND.- -Mayo ! Galway ! Kerry ! Dublin and Wicklo w (A i 'die i •) . Geogr. Distribution. — France. Germany. Austria and Galicia. Bohemia. Hungary. Italy. Norway. Sweden. Denmark. Bornholm. Finland (var.). Lapland. S. Russia. Greenland. Spitsbergen. Afghan- istan. Sumatra (var.). Abyssinia. New Zealand. United States. This species is widely distributed but by no means common. We figure a small form of it (PL LIX, fig. 4) which might almost stand as " forma minor " • length 34 /LI ; breadth 27*5 fj. ; breadth of isthmus 11 /u. Gutwinski has described a "forma minima' from Galicia with the following dimensions: — length 17-22 /u ; breadth 16-17 ju : breadth of isthmus 5 /u. Var. minutum Wittr. (PL LIX, figs. 6, 7.) C. undulatum Corda var. minutum Wittr. Skandiiiav. Desm. 1869, p. 11, t. i, f. 3 : Gotl. Ol. sotv. Alg. 1872, p. 59 ; De Toni, Syll. Alg. 1889, p. 973 ; Eoy & Biss. Scott. Desm. 1894, p. 177. C. crenatnm Ealfs var. alpinum Eacib. Nonn. Desm. Polon. 1885, p. 76, t. 11, f. H. C. alpinum (Eacib.) De Toni, Syll. Alg. 1889, p. 942 ; Schmidle in Hed- wigia, 1894, p. 89. U'rsinella alpina Ktmtze, Eevis. gen. plant. 1891, p. 924. Cells smaller, about 1£ times longer than broad; semicells subsemicircular, basal angles rounded, margin undulate, with 12-14 undulations. Length 21-28 p.; breadth 18-21 p.; l)readth of isth- mus 8'5-lG p.; thickness 12-13 p.. ENGLAND. — Strensall Common, X. Yorks ! (Turner). Leicestershire (Roy). SCOTLAND. — " Xot so common as the type ' (Roy fy Bissett). IEELAXD.- -Foxford, Maj^o ! lar Connaught, Galway ! Geogr. Distribution. — Germany. Sweden. Poland. 150 BEITISH DESMIDIACE.E. C. crenatum Ralfs var. alpinum Racib. is unquestionably the same Desmid as C. undulatum Corda var. minutum Wittr., and should without doubt be regarded as a variety of C. undulatum. It differs from the typical form of that species in the shape of the semicells and in the more numerous undulations. Yar. crenulatum (Nag.) Wittr. (PL LIX, figs. 11, 12.) ? Euastrum, crenulatum Ehrenb. 1839. E. (Cosmarium) crenulatum Nag. Gatt. einz. Alg. 1849, p. 120, t. 7 A, f. 7. Cosmarium crenulatum Breb. Liste Desni. 1856, p. 131 ; Schniidle, Beitr. Algenfl. Schwarzwald. u. Klieineb. 1893, p. 96, t. 4, f . 9 ; Beitr. alp. Alg. 1895, p 388. C. bioculatum Breb. b. crenulatum Eabenh. Flor. Eur. Alg. Ill, 1868, p. 163 ; De Toni, Syll. Alg. 1889, p. 933. C. undulatum Corda var. crenulatum (Ehrenb.) Wittr. Skanclinav. Desm. 1869, p. 11 ; Nordst. Desni. Brasil, 1870, p. 210 ; Wittr. Gotl. Ol. sctv. Alg. 1872, p. 59 ; Heimerl, Desm. alp. 1891, p. 599. C. Meneghinii Breb. forma crenulata Kichter in Wittr. & Nordst. Alg. Exsic. 1883, no. 566 ; Hansg. Prodr. Algenfl. Bohin. 1888, p. 195 ; Hoff in Nordst. Bornh. Desm. 1888, p. 197. Cells smaller, about 1^- times longer than broad; semicells quadrate-semicircular, with about 8 undula- tions including the basal angles. Length 29-30 /*; breadth 22-5-23 //,; breadth of isthmus 7-8*5 ft; thickness 13 /*. SCOTLAND. — Craig-an-Lochan, Perth ! Geogr. Distribution. — Germany. Bohemia. Switzer- land. Sweden. Bornholm. Spitzbergen. India. Brazil. This variety is distinguished from other forms of C. undu- latum bv the fewer number of undulations on each semicell. t/ In general aspect it closely resembles C. impressulum Elfv., a species with which it should be carefully compared. C'. Meneghinii Breb. forma tricrenata Turn. (Treshw. Alg. E. India/ 1893, p. 71, t, 8, f. 25) is stated by the author to be identical with Euastrum crenulatum Nag., but his figure is much nearer a form of C. impressulum Elfv. Var. Wollei West. (PI. LIX, figs. 8-10.) C. undulatum Corda var. crenulatum Wolle, Desm. U. S. 1884, p. 67, 1. 16, f . 10, 19 : Eoy & Biss. Scott. Desni. 1894, p. 177. C. undulatum Corda var. Wollei West. Alg. W. Ireland, 1892, p. 151. COSMARIUM. 151 Cells smaller, broadly elliptic, about 1J times as long as broad ; semicells subsemicircular, with 13 or 14 crenations in the margin. o Zygospore globose, furnished with long spines (or processes) with tridentate apices. Length 32-43 JJL; breadth 27-36 p.; breadth of isth- mus 10-13'5/x; diam. zygosp. without spines 34 /x, with spines 44-45 /*. ENGLAND.- -Near Bristol, Gloucestershire (Rolfs). IEELAND. — Xear Oughterard, Gal way ! Geogr. Distribution. — United States. This variety is distinguished from all the other forms of C. undulatum by the crenation of the margin, which is of precisely the same nature as that of Gosmarium speciosum Lund. The semicells are not inclined to be subquadrate as in var. minutum and var. crenulatum. The zygospore of C. undulatum figured by Ralfs in his ' British Desmids/ t. 15, f. 8, most certainly belongs to this variety. The empty semicells which he figures round the zygospore are crenate. 13. Cosmarium subundulatum Wille. (PL LIX, figs. 13-15.) Cosmarium undulatum (Corda) Kalfs var. tumidum Jacobs. Desni. Danem. 1876, p. 197, t. 8, L 18 ; Borge, Chlor. Norska Finmark. 1892, p. 10, t. 1, f. 8. Cosmarium subundulatum Wille, Norges Ferskv. Alg. 1880, I, p. 27, t. 1, f . 9 ; Boldt, Desm. Gronl. 1880, p. 17 ; Be Toni, Syll. Alg. 1889, p. 1051 ; Roy & Biss. Scott. Desm. 1894, p. 175 ; West & GK S. West, Alga-fl. Yorks. 1900, p. 81. Ursinella subundulata Ktintze, Kevis. gen. plant. 1891, p. 925. Cosmarium Nuttallii West, Alg. W. Ireland, 1892, p. 151, t. 21, f. 5. C. undidatum Corda var. subundulatum Borg. Fresliw. Alg. Ostgronl. 1894, p. 17, t. 1, f. 8 ; Schmidle, Alg. aus Sumatra, 1895, p. 303, t. 4, f . 9. Cells of moderate size, 1J times longer than broad, elliptic, deeply constricted, sinus very narrow, dilated at the apex; semicells semi-elliptic, basal angles rounded, apex commonly a little flattened, margins with about 12 undulations, and with two series of undulations within the margin corresponding to the peripheral ones. Side view of semicell ovate, apex 152 BRITISH DESMIDIACE^E. 5-undulate. Vertical view elliptic, ratio of axes about 1 : 1'5, with a broad tumour at the middle on each side, poles 5-undulate. Cell-wall very delicately punctate, and often furnished with a few minute scrobiculations more or less regularly disposed near the margin of the semicells. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 45-60 ^u ; breadth 32-39 ^ ; breadth of isthmus 15-16 /u ; thickness 23-27 /u. ENGLAND. — Angle Tarn, Cumberland ! Blea Tarn, Westmoreland ! Pilmoor, N. Yorks ! WALES.- -Llyn Idwal, Llyn-y-cwm-ffynon, and Capel Curig, Carnarvonshire ! SCOTLAND. — Xear Strathpeffer, Ross; Brin, Inver- ness ; Upper Powlair and Slewdrum, Aberdeen ; near Kingshouse, Argyll (Roy fy Bissett). Rliiconich, Sutherland ! IRELAND.- -Near Foxford, Mayo ! Ballynahinch, Lough Athry, Clifden, and near Ougliterard, Gralway ! Adrigole and Castletown, Kerry ! Geogr. Distribution. — Norway. Greenland. This species differs from C. undulatum in its proportionately longer cells, in the semi-elliptic shape of the semicells, and in the presence of the large protuberance in the centre of the semicells. There are usually a few minute scrobiculations near the margin of the semicells, more or less regularly arranged, but rather variable in different individuals and somewhat difficult of observation. 14. Cosmarium Cucumis (Corda) Ealfs. (PL LIX, figs. 18-20.) ? ? Cosmarium Cucumis Corda in Aim. de Carlsbad, 1835, p. 206, t. 2, f . 27. Cosmarium Cucumis Ealfs' Brit. Desm. 1848, p. 93., t. 15, f. 2 ; Arch, in Pritch. Iiifus. 1861 ; Rabenh. Flor. Europ. Alg. 1868, III, p. 161 ; Xordst. Desm. Spetsb. 1872, p. 36 ; Kirchn. Alg. Schles. 1878, p . 146 ; Wolle, Desm. U.S. 1884, p. 58, t. 15, f. 6-9 ; Nordst. Desm. Gronland, 1885, p. 9 [forma major] ; Cooke, Brit. Desm. 1886, p. 84, t. 36, f. 11 ; Nordst. Bornh. Desm. 1888, p. 202 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, p. 163; Alg. Eng. Lake Distr. 1892, p. 729; Roy & Biss. Scott. Desm. 1894, p. 44 ; Nordst. Index Desm. 1896, p. 91 ; West & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 69 ; Alg. N. Ireland, 1902, p. 33. COSMARIUM. 153 Euastrum (Cosmarium) Cucumis Nag-. Gatt. einz. Alg. 18-49, p. 114. Didymidium (Cosmarium) Cucumis Reinsch, Algenfl. Frank. 1867, p. 108. Cosmarium Cucumis a. typicum Klebs, Desni. Ostprenss, 1879, p. 30, t. 3, f. 11, 12, 15. Cosmaridium Cucumis Gay, Monogr. loc. Conj. 1884, p. 78, t. 2, f. 19; Hansg. Prodr. Algenfl. Bohm. 1888, p. 190. Co&marium Cucinnis 2. anglica Racib. Nonn. Desm. Polon. 1885, p. 70. Pleurotaeniopsis Cucumis Lagerh. Algol. Bidr. 1887, p. 197. Cells large, 1-J-lf times as long as broad, deeply constricted, sinus narrowly linear with a slightly dilated extremity ; semicells semi-elliptic or widely truncate- ovate from a broad base, both inferior and superior angles rounded, apex rounded or sometimes slightly truncate. Side view of seniicell obtusely ovate. Vertical view broadly elliptic or elliptic-oblong, ratio of axes about 1 : I'o. Cell- wall smooth. Chloroplasts 6 or 8 in each semicell, forming parietal, irregular bands extending from base to apex, and each contain- ing several pyrenoids. Zygospore unknown. Length 62-102 n; breadth 34-56 ^; breadth of isthmus 20-38 /u ; thickness 27-38 p. ENGLAND. — Cumberland ! Westmoreland (up to 2,400 ft.) ! (Ralfs). W., X., and E. Yorks ! Lanca- shire! Essex! Oxfordshire! Warwick (Wills). Gloucester (Ralfs). Surrey! Sussex (Balfs). Hants (Bennett). Devon (Bennett). Cornwall ! WALES. — Snowdon ! , Capel Curig ! (Cooke $• Wills), Llyn Idwal ! , Llyn Ogwen ! , Bethesda ! , Llyn-an- af on ! , Moelfre ! , and Yr Orsedd ! , Carnarvonshire. SCOTLAND. — General! (Roy fy Bissett). Outer Heb- rides ! Orkneys ! Shetlands ! IRELAND.- -Donegal ! Gralway ! Kerry ! Dublin and Wicklow ! (Archer). Down ! Geogr. Distribution.- -France. Germany. Switzer- land. Austria and Galicia. Poland. Hungary. Italy. Portugal. Norway. Sweden. Denmark. Bornholm. Finland. N. and S. Russia. Greenland. Spitzbergen. Nova Zembla. Siberia. Iceland. Faeroes. Azores. Burmah. Porto Rico. Brazil. Uruguay. Patagonia. C. Cucumis is somewhat variable both in size and in its 154 BRITISH DESMIDIACEJ:. relative proportions. In the typical form the apices of the semicells are very slightly (almost inappreciably) flattened and the sinus is fairly deep. The chloroplasts are very characteristic. They are parietal bands similar to those present in C. Ralfsii, but are broader with more serrated edges. The number of bands in each semicell is not constant, and each band possesses several small ellipsoidal pyrenoids. In the fAlg. of W. Ireland' p. 163, the zygospores of C. Cucumis were described as u globose and smooth," but we are now uncertain as to the identity of the species in question. It mav have been C. Sultcucumis or some other allied form, as a/ the measurements (length 54-57 fj.; breadth 30-31 /it) are not those of typical C. Cucumis. Var. helveticum Nordst. C. Cucumis var. helveticum Nordst. in Wittr. & Nordst. Alg. Exsic. 1880, No. 378 ; and in fasc, 21, 1889, p. 43 ; Eoy & Biss. Scott. Desm. 1894, p. 44. Cells smaller, semicells more rapidly attenuated towards the apex ; cell-wall densely and minutely scrobiculate. Length 48-56 M; breadth 26-36 p; breadth of isthmus 10-12 /LI; thickness 22-26 /u. ENGLAND.- -Delamere, Cheshire (Roy). Leicester- shire (Roy). WALES.- -Glyder Fawr and Pen-y-gwryd, Carnar- vonshire (Rot/). SCOTLAND.- -Inverness, Aberdeen, Kincardine (Roy fy Sis sett). Geogr. Distribution . — Switzerland. We have not seen this variety. Nordstedt states that it strongly resembles C. subquadratum Nordst. and C. variolatum Lund. Var. magnum Racib. (PL LIX, figs. 21, 22.) C. Cucumis "forma major noil tarn, prof uncle constricta quaru anglica, membraiia crassa/' Nordst. Desm. Arctose, 1875, p. 29, t. 8, f. 28; Boldt, Desm. Groulancl, 1888, p. 11 ; Borg. Bornholm. Desm.-fl. 1889, p. 146 ; Eoy & Biss. Scott. Desm. 1894, p. 44. C. Cucumis o.magna Eacib. Xonn. Desm. Polon. 1885, p. 70; West & G. S. West, Fresliw. Alg. Orkneys and Shetlands, 1905, p. 15 (sep.). COSMARIUM. 155 A large variet}r, almost twice as long as broad, and less deeply constricted than the type ; semicells with truncate or subtruncate apices ; cell-wall densely punctate, often thick. Length 98-107 M; breadth 53-66 n; breadth of isthmus 33-43 ju; thickness 38'5-46,u. ENGLAND. — Helvellyn. Westmoreland ! V SCOTLAND.--" Pretty common : (Roy fy Bissett). Skye, Inverness ! AY. of Kirkwall, Orkneys ! Geogr. Distribution.- -Bornholm. Spitzbergen. Green- land. 15. Cosmarium Subcucumis Schmidle. (PL LX, figs. 1-3.) Cosmarium siibcucumis Scliinidle, Beitr. Algenfl. Schwarzwald. u. Blieineb. 1893, p. 98, t. 4, f. 20-22 ; Nordst, Index Desm. 1896, p. 244; West & G-. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 69. Cells large, broadly elliptic, about If to If times as long as broad, deeply constricted, sinus linear and dilated towards the extremities (sometimes slightly open) ; semicells semi-elliptic, basal angles rounded, apex convex or somewhat flattened. Side view of semicell broadly elliptic. Vertical view elliptic, ratio of axes about 1 : 1'5. Cell-wall smooth. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. Length 54-78 /A; breadth 36-45 /x; breadth of isthmus 15-19 p. ; thickness 23— 26 /A. ENGLAND.- -Ogden Clough, Ilkley, and Cautley Spout, "W. Yorks ! Eslier West-end and Wimbledon Commons, Surrey ! Geogr. Distribution. — Germany. Galicia in Austria. The British specimens are not precisely like those originally described by Schmidle from Germany. The cells are rela- tively longer and the sinus is generally slightly open. The relative proportion of breadth to length in the British speci- mens is 1 : 1'79; that in the German specimens is 1 : 1*42. The species differs from C. Cucumis in its axile chloroplasts, each of which contains two rather large pyrenoids. 156 BRITISH DESMIDIACEJE. We give a figure of a rather peculiar specimen (PI. LX, fig. 4) in which the chloroplasts were neither axile nor parietal, but in an intermediate condition. In the shorter semicell the chloroplasts suggest a parietal disposition, whereas in the longer semicell there is an axile disposition. The external features of this specimen are also more in agreement with those of C. Cucumis. 16. Cosmarium microsphinctum Norclst. (PL LX, figs. 5-8.) Cosmarium microsphinctum Nordst. Desni. Ital. 1876, p. 33, t. 12, f. 9 ; "VVolle, Freshw. Alg. U.S. 1887, t. 60, f. 20, 21 ; Boldt, Desm. Gronl. 1888, p. 11 ; De Toni, Syll. Alg. 1889, p. 1005 ; West, Alg. Eng. Lake Distr. 1892, p. 724, t. 9, f. 32 ; Lutkem. Desm. Attersees, 1893, p. 551 ; Eoy & Biss. Scott. Desm. 1894, p. 168; Borg. Freshw. Alg Ostgron- land, 1894, p. 16, t. 1, f . 6 ; Nordst. Index Desm. 1896, p. 170 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 70. Ursinella microsphincta Kuntze, Eevis. gen. plant, 1891, p. 925. Dysphinctium microsiihinctum (Nordst.) Schmidle, Alg. Sumatra, 1895, p. 302. Cells small, elliptic, about 1^ times longer than broad, moderately constricted, sinus uniformly narrow and linear ; semicells semi- elliptic, sides convex, gradu- ally converging from an almost straight base to a rounded apex, basal angles subrectangular. Side view of semicell ovate. Vertical view rhomboid- elliptic, poles very slightly produced, ratio of axes about 1 : 1*38. Cell-wall very finely punctate. Chloro- plasts axile, each with one pyrenoid. Zygospore globose, furnished with processes arising from broad bases ; apices of processes bifurcate or tri- furcate. Length 86-39' 5 ju; breadth 25-27^; breadth of isthmus 14*5-18 M; thickness 18-20^; cliam. zygosp. without spines 20^, with spines 5-4 /u. ENGLAND.- -Heseltine Grhvll, Penyghent, and near Ilkley, W. Yorks ! Mickle Fell, N. Yorks ! SCOTLAND. — Ardtannes near Inverurie, Craigendinnie near Aboyne, and Presswhin in Cromar, Aberdeen (Roy $ BisseU). Geoc/r. Distribution.- France. Germany (var.). Austria and Gralicia. Italy. Faeroes. Greenland. Xova Zembla. Franz Joseph Land. United States. COSMARIUM. 157 This is a characteristic species which occurs amongst mosses on wet rocks in mountainous or alpine areas. In the British Islands it appears to be very rare. It is distinguished from C. pseiidopymmidatum Lund, and C. variolatum Lund, by its much shallower constriction, its rounded apices, its more densely punctate cell-wall, and by the tumour at each side of the vertical view. Forma parvula "Wille. (PI. LX, fig. 9.) C. microsphinctum Nordst. forma parvula Wille, Ferskv. Alg. Nov. Semlj. 1879, p. 38. t. 12, f . 22 ; Eoy & Biss. Scott. Desm. 1894, p. 168. Cells a little smaller and proportionately a little longer ; seniicells more attenuated to a narrower apex. Length 33 /i ; breadth 20 /a ; breadth of isthmus 7 /u ; thickness 15^. SCOTLAND. — Kemback near St. Andrews, Fife (Roy § Blssetf). Geogr. Distribution. — Nova Zembla. Var. majus Roy & Biss. (PL LX, fig. 10.) C. microsphinctum Nordst. var. majus Eoy & Biss. Scott. Desm. 1894, p. 168, t. 4, f. 7. About twice the size of the ordinary form. «/ Length 80 n ; breadth 52 ^ ; breadth of isthmus 35 /n. SCOTLAND. — Presswhin in Cromar, Aberdeen (Roy § Bissett). 17. Cosmarium morsum West. (PL LX, fig. 11.) Cosmarium morsum West, Alg. Eng. Lake Distr. 1892, p. 729, t. 9, f. 10; Nordst. Index Desm. 1896, p. 176. Cells rather small, almost twice as long as broad, slightly constricted, sinus widely open and semicircular; semicells semi-elliptic, basal angles rectangular. Side view of semicell subcircular, with the sides somewhat compressed. Vertical view very broadly elliptic, ratio of axes about 1 : 1'2. Cell-wall smooth. Zygospore unknown. 158 BRITISH DESMIDIACE^;. Length 40*5 n ; breadth 23 '2 /* ; breadth of isthmus 15*5 n ; thickness 20 '2 /LI. ENGLAND. --Near Bowness, Westmoreland ! This species is characterized by the curious excavated sinus and by its relatively great thickness. We have seen no living specimens of it. 18. Cosmarium Phaseolus Breb. (PI. LX, figs. 12-14.) Heterocarpella Phaseolus Breb. in Clieval. microscop. et iisage, 1839, p. 272. Cosmarium Phaseolus Breb. in Menegh. Synops. Desm. 1840, p. 220; Ealfs, Brit. Desm. 1848, p. 106, t. 32, f. 5 ; Breb. Liste Desm. 1856, p. 131; Arch, in Pritch. Infus. 1861, p. 732; Rabenh. Flor. Europ. Alg. Ill, 1868, p. 166; Kirchn. Alg. Schles. 1878, p. 153; Wolle, Desm. U.S. ]884, p. 81, t. 18, f. 28-32 ; Cooke, Brit. Desm. 1886, p. 88, t. 37, f . 3 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 201 ; De Toni, Syll. Alg. 1889, p. 1001 ; West. Alg. N. Wales, 1890, p. 288 ; Add. Alg. W. Yorks. II, 1891, p. 245 ; Alg. W. Ireland, 1892, p. 145 ; Alg. Eng. Lake Distr. 1892, p. 725 ; "Boy & Biss. Scott. Desm. 1894, p. 171 ; Nordst. Index Desm. 1896, p. 199 ; West & G. S. West, Alg. S. England, 1897, p. 486 ; Alga-fl. Yorks. 1900, p. 70; Alg. N. Ireland, 1902, p. 33. C. Phaseolus a. typicum Klebs, Desm. Ostprenss. 1879, p. 35. Euastrum (Cosmarium} Phaseolus Gay, Moiiogr. loc. Conj. 1884, p. 59. Ursinella Phaseolus Kuntze, Revis. gen. plant. 1891, p. 925. Cells small, as long as broad, deeply constricted, sinus narrow with a dilated extremity ; semicells rather narrowly reniform. Side view of semicell sub- circular, with a slight protuberance at the middle on each side. Vertical view narrowly elliptic, ratio of axes about 1 : 2, with a small protuberance at the middle on each side. Cell-wall minutely punctate. Chloroplasts axile, with one pyrenoid. Zygospore globose, densely aculeate, aculei arising from broad bases. Length 29-35 n ; breadth 26-36 /i; breadth of isthmus 9-11 ^; thickness 19-22 /n; cliam. zygosp. without spines 33 /<, with spines 47 M- ENGLAND.- -Westmoreland (Bissett). W., N., and E. Yorks ! Middlesex ! Surrey ! Devon ! Cornwall ! (Ealfs). WALES. — Capel Curig ! (Cooke ^ Wills), Llyn Ogwen ! , COSMARIUM. 159 and Yr Orsedd! , Carnarvonshire. Dolgelly, Merioneth (Ralfs). SCOTLAND.- -Ross, Inverness ! , Aberdeen, Kincardine, Forfar ! , Perth ! , Argyll, Arran, Fife (Roy $ Bissett). Sutherland ! Kirkcudbright ! IRELAND.- -Donegal! G-alway! Kerry! Dublin and Wicklow (Arrln't']. Geocjr. Distribution. — France. Belgium. Germany. Austria (var.) and Galicia. Poland (var.). Hungary. Bosnia. Italy. Norway. Sweden. Denmark. Born- holm. X. and S.Russia. Siberia. Greenland. Faeroes. Spitzbergen. India. New Zealand. Australia (form) . Central and E. Africa. United States. Porto Rico. C. Phaseolus should be carefully compared with. C. depressum (Xag.) Lund., C. subtumidum Nordst., and varieties of these species. Apart from differences in the form of its semicells, it can be distinguished at once by the small but prominent protuberance on each side of the vertical view. A Voile observed the zygospore from the United States. It is a widely distributed species, but in the British Islands it is distinctly rare. Forma minor Boldt. (PL LX, fig. 15.) C. Phaseolus forma minor Boldt, Siber. Chlorophy. 1885, p. 102; Desni. Gronland, 1888, p. 15 ; West and G-. S. West, Alg. S. England, 1897, p. 486. Cells smaller than in the typical form. Length 20*4-21 p,; breadth 18/x,; breadth of isthmus 5*5-6 p.; thickness 11'5-14'4^. ENGLAND.- -Grrmspound, Devonshire ! Geoyr. Distribution. — Siberia, Greenland. Var. elevatum Xordst. (PI. LX, figs. 16, 17.) C. Phaseolus var. elevatum Nordst. Norges Desni. 1873, p. 17, t. 1, f . 5 ; Desm. Arctose, 1875, p. 24; Wille, Sydamerik. Algfl. 1S84, p. 31 ; Boldt, Siber. Chlorophy. 1885, p. 102; Hansg. Prodr. Algenfl. Bohm. 1888, p. 251 ; Boldt, Desm. Gronland, 1888, p. 15 ; De Toni, Syll. Alg. 1889, p. 1001 ; Schmidle, Beitr. Algenfl. Schwarzwald. 11. Rheineb. 1893, p. 102, t. 5, f. 11 ; Eoy & Biss. Scott. Desm. 1894, p. 171 ; Schmidle, Beitr. alp. Alg. 1895, p. 456 ; West & G. S. West, Alg. N. Ireland, 1902. p. 33. Semicells generally hexagonal-elliptic, apex truncate- convex. 160 BRITISH DESMIDIACEJC. Length 26'4-28'S p. ; breadth 25-2-30 p, ; breadth of isthmus 7-10 /u ; thickness 14-4-17 p. SCOTLAND.- -Near Ballater, Aberdeen ; G-leii Dye, Kincardine; Rannoch, Perth (Roy fy Bissett). IRELAND.- -Lough Machugh, Donegal (abundant) ! Geogr. Distribution.- -Germany. Glalicia in Austria (form). Norway. Sweden. Bornholm. Finland. Iceland. Faeroes. Spitsbergen. Uruguay. This variety very closely resembles C. subtumidum JSTordst. var. Klebsii (G-utw.) W. & G-. S. West, especially in the front view, but it can be recognized by the protuberance on each side of the vertical view. 19. Cosmarium tumidum Lund. (PL LX, fig. 18.) Cosmarium tumidum Lund. Desm. Siiec. 1871, p. 45, t. 3, f. 16 ; Wolle, Desni. U.S. 1884, p. 61, t. 15, f. 23 ; Boldt, Desm. G-ronland, 1888, p. 15 ; De Toni, Syll. Alg. 1889, p. 955 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. Eng. Lake Distr. 1892, p. 725 ; Roy & Biss. Scott. Desm. 1894, p. 177 ; Nordst, Index Desm. 1896, p. 262. C. pseudonitidulum Nordst. var. majus E-eiiiscli, Contrib. Alg. et. Fung. 1875, p. 88, t. 12, f. 7. Ursinella tumida Knntze, Eevis. gen. plant. 1891, p. 926. Cells rather small, a little longer than broad, deeply constricted, sinus narrow, widening outwards; semi- cells subsemicircular- elliptic, apices broadly convex. Side view of semicell circular. Vertical view elliptic - rhomboid, widely tumid at the middle on each side, ratio of axes about 1 : 1*35. Cell-wall finely punctate, punctulations larger in the centre of the semicells. Chloroplasts axile, each with one pyrenoid. Zygospore unknown. Length 33-37 /*; breadth 27-32 /u; breadth of isthmus 8-9 -5 // ; thickness 23 ju. WALES.- -Capel Curig, Carnarvonshire! SCOTLAND. - • Slewdrum, Upper Powlair, Aboyne, Castletoii, and Glen Clunie, Aberdeen ; near Menmuir, Forfar; Folotry, Perth (Roy ^ Bissett). IRELAND.- -Near Oughterard, Galway ! Geogr. Distribution. — • France. Germany (form). COSMARIUM. 161 Xorwav. Sweden. Denmark. Poland. N". Russia. fc Finland. Greenland. United States. This rare species stands near to C. Phaseolus Breb., but is distinguished by its proportionately greater length compared with its breadth, by the straighter and less reniform base of the semicells, and by the broadly tumid (ventricose) sides of the vertical view. Lundell also states that the chloroplasts are like those of C. moniliforme (Turp.) Ralfs, consisting of a number of lobes radiating from a central pyrenoid. Forma subrectangularis /. nov. (PL LX, fig. 19.) Semicells distinctly subrectangular with rounded angles. Length 32' 5 /i ; breadth 2 7' 5 /n ; breadth of isthmus 11*2 /i ; thickness 22 /u. IRELAND. — Ballynahinch, G-alway ! This form is characterized by the shape of its semicells as seen in the front view. The punctulations on the cell-wall are larger in the centre of the semicells as in the typical form. 20. Cosmarium Trafalgaricum "\Vittr. (PL LX, fig. 20.) • Cosmarium Trafalgaricum Wittr. in "Wittr. & Norclst. Alg. Exsic. 1877, no. 81 ; and in fasc. 21, 1889, p. 44 ciirn fig. xylogr. ; Cooke, Brit. Desm. 1886, p. 89, t. 43, f . 7 (figure incorrect) ; De Toni, Syll. Alg. 1889, p. 1054. Ursinella Trafalgarica Knntze, Revis. gen. plant. 1891, p. 925. Cells small, about 1-J- times longer than broad, deeply constricted, sinus linear, widening outwards ; semicells subreniform with a rather flattened base, middle of apex emarginate. Side view of semicell spherical, with a small protuberance on each side. Vertical view elliptic, with a protuberance at the middle on each side, ratio of axes (without protuberances) about 1:2. Cell- wall smooth. Zygospore unknown. Length 24-26 p.; breadth 20-21 p. ; breadth of isth- mus 6-7 n ; thickness 13-14 /^. ENGLAND. — In the fountains, Trafalgar Square, London (WittrocJc; 1872). VOL. II. 11 162 BRITISH We have not seen this species, nor has it been observed since its original discovery by Wittrock. It seems to be well characterized by its emarginate apices and its small central protuberance. Its nearest ally is perhaps C. Phaseolus Breb. 21. Cosmarium melanosporum Arch. (PL LX, figs. 21-23.) Cosmarium melanosporum Arch, in Ann. Mag. Nat. Hist. 1883, 5th ser. XII, p. 124 ; Cooke, Brit. Desm. 1887, p. 188 ; De Toni, Syll. Alg. 1889, p. 1055 ; Roy & Biss. Scott. Desm. 1894, p. 167, t. 1, f . 14 ; West & G. S. West, Alg. N. Ireland, 1902, p. 42. Ursinella melanospora Kuntze, E-evis. gen. plant. 1891, p. 167. Cells small, as long as broad, or sometimes a little longer than broad, deeply constricted, sinus narrow, widening outwards ; semicells transversely oblong, basal angles well rounded, upper angles more rounded, apex broadly convex. Side view of semicell circular. Vertical view elliptic, ratio of axes about 1 : 1*7. Cell- wall smooth. Zygospore globose and smooth, the wall of a very dark brown colour, becoming black. Length 15-19 /x; breadth 15-19 /x; breadth of isthmus 5-6*7 /x; thickness 7-9'6//,; diam. zygosp. 23-25-5 p,. ENGLAND. — Leicestershire (Roif) . WALES.- -Bettws-y-coed, Capel Curig, Grlyder Fawr, and Pen-y-gwryd, Carnarvonshire (Roy). SCOTLAND. — Generally distributed (Roij § Bissetf). Outer Hebrides ! IRELAND.- -Dublin and Wicklow (Archer). Lough Derryadd, Armagh ! Roy states that this species conjugates abundantly in Scotland, and may be readily recognized by the smooth, globular, very dark zygospore. We have only seen the zygospores from the Outer Hebrides and from Ireland. C. melanosporum stands very near to G. tenue Arch., but is distinguished by its more inflated semicells and by the dark colour of the zygospore. The constriction is not so deep in C. melanosporum as it is in C. tenue, and the vertical view is more broadly elliptic. cosMARTinr. 163 22. Cosmarium asphserosporum Nordst. (PI. LX, figs. 24, 25.) Cosmarium Schliephackeanum Rabenh. forma spetsbergensis Nordst. Desm. Arctoae, 1875, p. 24, t. 7, f. 15 ; Cooke, Brit. Desm. 1886, p. 92, t. 37, f . 10 ; Eoy & Biss. Scott. Desm. 1894, p. 174. C. asphserospomm Nordst. in Wittr. & Nordst. Alg. Exsic. 1879, no. 268 ; fasc. 21, 1889, p. 49; West & G. S. West, Alga.-fl. Yorks. 1900, p. 74. Ursinella asphserospora Kuntze, Revis. gen. plant. 1891, p. 924. Cells small, about as long or not quite as long as broad, moderately constricted, sinus widely open, sub- rectangular with an obtuse apex ; semicells broadly cuneate, with a widely-truncate apex and rounded angles. Side view of semicell obovate-subcircular from a broad base. Vertical view subrhomboid-elliptic, with a scarcely- evident, depressed wart at the middle on each side, ratio of axes about 1 : 1*27. Cell-wall smooth and colourless. Zygospore smooth, subrectangular-oblong, some- times elliptic or somewhat irregular, angles rounded, longer sides convex in the middle, shorter sides retuse; side view elliptic; end view circular; cell-wall lead- coloured. Length 10-13 //, ; breadth 12-13 /* ; breadth of isth- mus 7-8/x,; thickness 9-10 p; length of zygospore 21-22 p. ; breadth of zygospore 14-18 /x. ENGLAXD. — Penvsrhent, W. Yorks ! €/ O SCOTLAND. — Inverness, Aberdeen, Kincardine, Forfar, Perth, Stirling, Argyll ; zygospores from Dinnet, Aberdeen, and Kerloch, Kincardine (Rot/ fy Bissett). Geogr. Distribution.- -Norway. Sweden. Spitsbergen. Xova Zembla. Xew Zealand (var.) United States. This species is distinguished from C. bioculatum Breb. and C. tenue Arch, by its much shallower constriction and widely- open sinus, by the subtruncate apices, by the form of the vertical view,, and by the characteristic shape of the zygo- spore. It differs from C. inconspicuum West & Gr. S. West in its relatively greater breadth, its broader, subtruncate apices, its rhomboid vertical view, and its rectangular zygospore. 164 BRITISH DESMIDIACE2E. Var. strigosum Nordst. (PL LX, figs. 26, 27.) C. asphserosporuni Nordst. var. strigosum Nordst. in Wittr., Nordst. et Lagerh. Alg. Exsic. 1896, No. 1264 ; Bot. Notiser 1897, p. 86, cum fig. xylogr. ; West & G. S. West, Alg. S. England, 1897, p. 486. Cells witli a narrower isthmus and consequently with a deeper sinus, apices flatter; vertical view elliptic with no trace of median inflation. Length 10-11 /A; breadth 8-10 /x, ; breadth of isthmus 3*5 /z, ; thickness 5 p. ENGLAND. — Puttenham Common, Surrey ! Geogr. Distribution. — Sweden. This variety differs from C. bioculatum Breb. in its smaller size, its more open sinus, and its broad, truncate apices. From C. bioculatum var. hians it is distinguished by its smaller size, its straighter apices, its less-rounded lateral angles, and its smooth cell-wall. 23. Cosmarium inconspicuum West & G-. S. West. (PL LXI, figs. 1, 2.) Cosmarium inconspicuum West & G. S. West, New and Int. Freshw. Alg. 1896, p. 154, t. 4, f. 45 ; Alg. S. England, 1897, p. 486 ; Alga-fl. Yorks. 1900, p. 74 ; Alg. N. Ireland, 1902, p. 34. Cells minute, about 1-g- times longer than broad, moderately constricted, sinus open, subrectangular, with a rounded apex; semicells transversely elliptic, apices broadly convex, almost subtruncate. Side view of semicell subcircular. Vertical view elliptic, ratio of axes about 1 : 1*7. Cell-wall smooth and colourless. Chloroplasts axile, each with one pyrenoid. Zygospore ovoid, with a smooth and colourless wall. Length 13-5-14-6 /u; breadth 9*5-12 ,u; breadth of isthmus 4*8-6*5 ju; thickness 7-7*6 ft; cliam. zygosp. 1 4-5-17 fi. ENGLAND. — Bog two miles S. of Clapham, W. Yorks ! Mitcham Common, Surrey (with zygospores) ! Treme- thick Moor, Cornwall ! IRELAND. — Grlendoan and Lough G-artan, Donegal ! This species is a near ally of C. tenue Arch., C. tinctum Ralfs, and C. minutissimum Arch., all of which have smooth COSMARIUM. 165 zygospores. It can be recognized from all these species by the form of its cells alone. Its open sinus, rounded at the apex, is characteristic, and the chloroplast is furnished with a number of distinct lobes. 24. Cosmarium bioculatum Breb. (PI. LXI, figs. 3-7.) Heterocarpella bioculata Breb. Alg. Falaise, 1835, p. 56, t. 7 [in part only]. Cosmarium bioculatum Breb. in Ralfs' Brit. Desm. 1848, p. 95, t. 15, f. 5 In part ?] ; Arch, in Pritch. Inftis. 1861, p. 731 ; Eabenh. Flor. Europ. Alg. Ill, 1868, p. 163 ; Delp. Desm. subalp. 1877, p. 1, t. 7, f . 1-4 ; Kirchn. Alg. Schles. 1878, p. 147 ; Cooke, Brit. Desm. 1886, p. 89, t. 37, f . 6 ; Haiisg. Prodr. Algenfl. Bohui. 1888, p. 193 ; De Toni, Syll. Algar. 1889, p. 933 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, p. 146 ; Alg. Eng. Lake Distr. 1892, p. 725 ; Roy & Biss. Scott. Desm. 1894, p. 42 ; Xordst. Index Desm. 1896, p. 61 ; West & G-. S. West, Alg. S. England, 1897, Ip. 486 ; G. S. West, Alga-fl. Canibs. 1899, p. 115 ; West & G. S. West, Alga-fl. Yorks. 1900, p. 73 ; Alg. N. Ireland, 1902, p. 34; Scott. Freshw. Plankton, I, 1903, p. 526; Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 484. Didymidium (Cosmarium) bioculatum Reinsch. Algenfl. Frank. 1867, p. 107 [in part]. Cosmarium Phaseolus Breb. b. bioculatum Klebs, Desni. Ostpreuss. 1879, p. 35. Euastriim (Cosmarium) bioculatum Gay, Monogr. loc. Conj. 1884, p. 57. Ursinella bioculata Kuntze, Revis. gen. plant. 1891, p. 924. Cells minute, about as long as broad, deeply con- stricted, sinus narrow towards the apex and widening outwards ; semicells transversely oblong-elliptic, both base and apex flattened, sides rounded. Side view of semicell subcircular. Vertical view oblong-elliptic, ratio of axes about 1:2. Cell-wall smooth and colour- less. Chloroplasts axile with one pyrenoid. Zygospore globose, furnished with conical, blunt spines, from 9 to 11 of which show in the periphery. Length 15-21 M ; breadth 15-21 /LI ; breadth of isthmus 4'8-6*7/i; thickness 6-9'5/u; diam. zygosp. without spines 15-19 /u; with spines 22 ' 5-28 /i. ENGLAND. — Westmoreland! (Ralfs). W., N., and E. Yorks! Lancashire! (Ralfs). Leicestershire (Roy). Cambridgeshire! Warwick (Wills). Gloucestershire (Rolfs). Middlesex! Surrey (zygospores from Putten- ham Common) ! Sussex (Ralfs). Kent (Ralfs). Cornwall ! 166 BRITISH DESMIDIACEJE. WALES. — Fairly general in Carnarvonshire and Merioneth ! SCOTLAND.- -Sutherland !, Inverness, Aberdeen, Kin- cardine, Forfar !, Perth ! (Boy $ Bissett). At 3,500ft. on Lochnagar, Aberdeen ! Not uncommon in the plankton ! Outer Hebrides ! Orkneys ! Shetlands ! IRELAND.- -Donegal ! Mayo ! G-alway ! Kerry ! Dub- lin and Wicklow (Archer). Londonderry ! Down ! Armagh ! Geogr. Distribution. — France. Germany. Austria and Galicia. Poland. Hungary. Italy. Bosnia. Finland. Norway. Sweden. S. Russia. Siberia. Greenland. Spitzbergen. Nova Zembla. Central China. New Zealand (var.). Central Africa. Azores. United States. C. bioculatum is one of the most generally distributed of the small, smooth species of the genus. It is distinguished at once from all its allies by the spiny zygospore. The spines are stout, very blunt,, and not very numerous,, from nine to eleven being visible around the periphery of the spore. The semicells are somewhat narrowly elliptic or elliptic- oblong-, and the sinus is slightly open. Forma depressa Schaarschm. (PI. LXI, figs. 8, 9.) C. bioculatum Breb. forma depressa Schaarschm. Magyar. Desni. 1883, p. 270, t. 1, f . 10 ; De Toni, Syll. Alg. 1889, p. 934 ; West, Alg. Eng. Lake Distr. 1892, p. 725 ; Alg. S. England, 1897, p. 486. Cells subquadrate, with rounded angles, sinus open ; semicells transversely oblong with broadly flattened apices; vertical view oblong, sides parallel and poles rounded. Length 14*5-20 p.; breadth 17-18 p.. ENGLAND.- -Brother's Water, Westmoreland ! Epping Forest, Essex ! Keston Common, Kent ! Geofjr. Distribution. — Galicia in Austria. Hungary. Kew Zealand. Var. hians West & G. S. West. (PI. LXI, figs. 10, 11.) C. Uoculatum Breb. var. hians West & G. S. West, Alg. S. England, 1897, p. 486, t. 6, f. 24. COSMARIUM. 167 Cells with the sinus more open, somewhat conical with a subacute apex ; lower margins of semicells convex, apices straight or very slightly retuse. Cell- wall distinctly but minutely punctate. Length 17-19/>t; breadth 15-18/x; breadth of isth- mus 3'5-4ju; thickness 7'5-8'5/x. ENGLAND. — Putteiiham and Thursley Commons, Surrey ! This variety comes nearest to C. bioculatum Breb. var. excauatum Gutw.; but is proportionately shorter, with a more acute sinus, and the apices of the cells are straight or slightly retuse. The cell-wall is also distinctly punctate. 25. Cosmarium tenue Arch. (Plate LXI, figs. 12-15.) Cosmarium tenue Arch, in Quart. Jonrii. Micr. Sci. 1868, p. 293 ; Cooke, Brit. Desni. 1886, p. 92 ; West, Alg. W. Ireland, 1892, p. 147, t, 20, f . 25 ; Johns. Bare Desni. U.S. I, 1894, p. 288 ; Nordst. Index Desm. 1896, p. 251 ; West & G. S. West, Alg. N. Ireland, 1902, p. 34. C. ellipsoideum Elfv. forma minor Anderss. Sverig. Chlor. 1890, p. 16, t. 1, f. 9. Cells minute, about as long as broad, deeply con- stricted, sinus linear, opening outwards ; semicells transversely elliptic, apices slightly convex. Side view of semicell circular. Vertical view elliptic, ratio of axes about 1 : 1*8. Cell-wall smooth and colourless. Chloroplasts axile, each with one pyrenoid. Zygospore globose and smooth. Length 14-16^; breadth 13'5-15-5^; breadth of isthmus 3'5-4'5 p ; thickness 8'5 /n ; diam. zygosp. 22-23 fi. IRELAND.- -Lough Derryclare, and lakes E. of Lough Bofin, Galway (with zygospores) ! Dublin and Wicklow (Archer). Slieve Donard, Down! Geogr. Distribution- -Germany (form). Galicia in Austria. Sweden. United States. C. tenue Arch, may very easily be confused with C. biocu- latum Breb., but the semicells are more elliptic and the zygospore is quite smooth. 168 BRITISH DESMIDIACE/E. The Desmid figured by Wolle (' Desm. U.S.' 1884, t. 15, f. 22) as C. bioculatum is most probably a form of (7. tenue as it lias a smooth zygospore. Johnson ('Rare Desm. U.S/ I, 1894, p. 288) also states that C. tenue is common almost everywhere in the United States, and is often found in quantity and usually with zygospores. 26. Cosmarium tinctum Ralfs. (PL LXI, figs. 16-18.) Cosmarium tinctum Ralfs, Brit. Desni. 1848, p. 95, t. 32, f. 7 ; Arch, in Pritch. Infus. 1861, p. 731 ; Kirchn. Alg. Schles. 1878, p. 148 ; Wolle, Desm. U.S., 1884, p. 61, t. 16, f. 31 ; Cooke, Brit. Desm. 1886, p. 90, t. 37, f . 7 ; Hansg. Prodr. Algenfl. Bohrn. 1888, p. 248 ; De Toni, Syll. Alg. 1889, p. 942 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, p. 146 j Alg. Eng. Lake Distr. 1892, p. 725 ; Eoy & Biss. Scott. Desm. 1894, p. 176; Nordst. Index Desm. 1896, p. 255; West & GL S. West, Alg. S. England, 1897, p. 486; Alga-fl. Yorks. 1900, p. 73 ; Alg. N. Ireland, 1902, p. 34. Sphserozosma tinctum Eabenh. Flor. Europ. Alg. Ill, 1868, p. 150. Ursinella tincta Kuntze, Revis. gen. plant. 1891, p. 925. Cells minute, a little longer than broad, moderately constricted, sinus narrow towards the apex but open outwards; semicells elliptic. Side view of semicell subcircular. Vertical view elliptic, ratio of axes about 1 : 1*8. Cell-wall smooth and of a reddish-brown colour. Chloroplasts axile, with one pyrenoid. Zygospore subquadrate, with rounded angles and retuse sides ; cell- wall smooth. Length 10-15^; breadth 7'5-ll'6^; breadth of isthmus 4*5-8*4 ^t; thickness 5-9 /u ; cliam. zygosp. 11-15/4. ENGLAND. — Cumberland ! Westmoreland ! W., IN"., and E. Yorks ! Cheshire (Roy). Essex ! Warwick (Wills). Surrey! Sussex (Ralfs). Kent! Hants! Devon ! Cornwall ! (Ralfs). WALES. — Fairly general in Carnarvonshire ! SCOTLAND. --General ! Zygospores from Aberdeen and Kincardine (Roy $• Bissett). Outer Hebrides ! Shetlands ! IRELAND.- -Donegal ! Mayo ! Galway (zygospores from near Eoundstone) ! Kerry ! Dublin and Wicklow ! (Archer). Armagh ! COSMARIUM. 169 Geogr. Distribution. — France. Belgium. Germany. Austria and Gralicia. Hungary. Italy. Portugal. Norway. Sweden. Denmark. Bornholm. Finland. N. Russia. Faeroes. Greenland. Nova Zembla. New Zealand. Australia. E. Africa. Azores. United States. "W. Indies. Brazil. Paraguay (var.). Pata- gonia. C. tinctum is distinguished from both C. bioculatum and C. tenue by its proportionately longer cells which are not so deeply constricted. The semicells are more broadly elliptic, the sinus is more open,, and the cell-wall is generally of a pale yellow or yellow-brown colour. The subquadrate form of the zygospore is also characteristic of the species. It is a widely-distributed species and can sometimes be obtained in quantity in collections from boggy districts. The cell-wall is not invariably tinted, colourless individuals being' occasionallv met with. Wille has described a form t from Norway (vide ' Norges Ferskv. Alg./ 1880, p. 36, t. 1, f. 22) in which the cell-wall is very delicately punctate, and Borge reports the occurrence of the same form in Greenland. Nordstedt has described a trigonal form from New Zealand, in which the vertical view is triangular with rounded angles and slightly convex sides (vide ' Fresh w. Alg. N. Zeal./ 1888, p. 61, t. 3, f. 16). Var. intermedium Nordst. (PI. LXI, figs. 19, 20.) C. tinctum Ralf s, var. intermedium Nordst. in Botan. Notis. 1887, p. 162 ; Fresliw. Alg. N. Zeal. 1888, p. 61, t. 3, f. 17 ; De Toni, Syll. Alg-. 1889, p. 9-13 ; Borge, Chlorophy. Norska Finmark. 1892, p. 13 ; West, Alg. Eng. Lake District, 1892, p. 725. Semicells with the sinus not narrowed towards the apex; vertical view with a slight tumidity at the middle on each side ; cell-wall often colourless. Length 11-15 /n ; breadth 10-12^; breadth of isthmus 6-8 ^ ; thickness 8-9 p. ENGLAND. — Borrowdale, Cumberland ! Geogr. Distribution. — Norway. New Zealand. This variety is intermediate in character between C. tinctum and C. aspherosporum . 170 BRITISH DESMIDIACE.E. 27. Cosmarium flavum Roy & Biss. (PI. LXI, figs. 21, 22.) Cosmarium flavum Eoy & Biss. Scott. Desm. 1894, p. 101, t. 2, f. 17 : Nordst. Index Desni. 1896, p. 124. Cells rather small, about as long as broad, deeply constricted, sinus narrow towards the apex but opening outwards ; semicells elliptic-oblong with a somewhat flattened apex. Side view of semicell subglobose. Vertical view elliptic, ratio of axes about 1 : 1*7. Cell- wall smooth and of a yellow colour. Zygospore globose and smooth. Length 32/x; breadth o2/x; breadth of isthmus 10 fji ; thickness 15'5 JJL ; diam. zygosp. 40 ft. SCOTLAND. • Loch Inver, Sutherland; Scotston, Birsemore, Craigendinnie, Dinnet, Dawin, Auchnerran, and Grlen Clunie, Aberdeen ; Crathes, Cammie, and Dalbrake, Kincardine (Roy $ Bissett). We have not seen this species, which. Roy & Bissett record as " rare " in Scotland. It appears to he very closely related to Cosmarium contractum forma Jacobsenii and C. contractual var. ellipsoideum, from each of which it chiefly differs in the cells being more flattened at the apices and in the yellow tint of the cell-wall. 28. Cosmarium contractum Kirchn. (PI. LXI, figs. 23-25, 34.) Cosmarium contractum Kirchn. Alg. Schles. 1878, p. 147 ; Wolle, Desm. U.S. 1884, p. 63, t. 16, f. 1 ; t, 50, f. 24 ; De Toni, Syll. Alg. 1889, p. 949; West, Alg. N. Wales, 1890, p. 291 ; Alg. W. Ireland, 1892, p. 160 ; Alg. Eng. Lake Distr. 1892, p. 729 ; Eoy & Biss. Scott. Desm. 1894, p. 44 ; West & a. S. West, Alg. Madag. 1895, p. 70, t. 8, f . 5 ; Nordst, Index Desm. 1896, p. 80 ; West & G. S. West, Welw. Afric. Freshw. Alg. 1897, p. 175 ; Alg. S. England, 1897, p. 491 ; Freshw. Chlorophy. Koh Chang. 1901, p. 91; Alga-fl. Yorks. 1900, p. 74; Alg. N. Ireland, 1902, p. 40; Scott. Freshw. Plankton I, 1903, p. 526; Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 483. C. contractum a. silesiacum Racib. Xonn. Desm. Polon. 1885, p. 84. Ursinella contracta Kuntze, Eevis. gen. plant. 1891, p. 924. Cells rather small, about 1-J times longer than broad, very deeply constricted, sinus narrow towards the apex, rapidly widening outwards; semicells sub-elliptic, COSMAKIUM. 17 L ventral margin always more convex than the dorsal margin. Side view of semicell circular. Vertical view elliptic, ratio of axes 1 : 1'57. Cell-wall colourless and finely punctate. Chloroplasts axile, with one central pyrenoicl. Zygospore globose or angular-globose, smooth. Length 34'5-41/x; breadth 25-3 1/x; breadth of isthmus 7-8* 7 ft; thickness 18-19 /x; diam. zygosp. 31*5—35 JJL. ENGLAND. — Bowness, Westmoreland ! Widdale Fell, W. Yorks ! Pilmoor, X. Yorks ! Pnttenham Common, Surrey ! WALES. — Llyn Bodgynwydd, Capel Curig, and Llyn- y-cwm-ffynon, Carnarvonshire ! SCOTLAND.- -Near Alford, and south of Birsemore, Aberdeen; Buchaiity, Perth (Roy § Bissett). Khi- conich, Sutherland ! Xot uncommon in the plankton of Sutherland, Inverness, Ayrshire, and the Outer t> Hebrides ! IRELAND.- -Lough Gartan and near Lough Magrath, Donegal ! Ballynahinch, Clifden, and Lough Aunierin, Galway ! Cromagloun, Tore Mt., and Adrigole, Kerry ! Lough Derryadd, Armagh ! Geoc/r. Distribution --QeYmany. Galicia in Austria. Poland. Xorway. India. Ceylon. Burmah. Siam. Australia. Central Africa. Madagascar. United States. Patagonia. C. contraction is a somewhat rare British species, although it sometimes occurs in abundance in the plankton. It is very deeply constricted, the isthmus forming a narrow neck, and the sinus is widely open. The semicells in the front view are subelliptic in form, the low^er margin being more convex than the upper one. The Desmicl described and figured by Turner ('Freshw. Alg. E. India/ 1893, p. 48, t, 7, f. 38, t. 9, f. 21) as C. con- tractum var. punctatum does not belong to this species. Forma Jacobsenii (Roy) nol. (PL LXI, f. 26.) Cosmarium moniliforme (Turp.) Ealfs forma elliptica Nordst. Norges. Desm. 1873, p. 22. C. moniliforme Jacobs. Desm. Daneni. 1876, p. 200, t. 8, f. 24. 172 BRITISH DESM1DIACE.E. 0. Jacobsenii Roy in Biss. Desni. Windermere, 188-4, p. 194 ; Cooke, Brit. Desm. 1887, p. 120, t. 43, f. 3 ; Nordst. Bornli. Desm. 1888, p. 200 ; Roy & Biss. Scott. Desm. 1894, p. 168. Cells almost 1^ times as long as broad, sinus open but rounded at the apex; semicells more equally elliptic or oblong-elliptic. Length 28-45 /A ; breadth 18-27 /n; breadth of isth- mus 4* 5-7 *5 yu. ENGLAND. — Near Bowness, Westmoreland (Bissett). SCOTLAND. — Slewdrum, Presswhin, Logie-Coldstone, and Grlen Clunie, Aberdeen ; Crathes, and Dalbrake in Strachan, Kincardine (Roy $' Bissett). Geogr. Distribution.- -Germany. Gralicia in Austria. Norway. Sweden. Denmark. Bornholm. Central Africa. This form is of the same relative length and breadth as typical (7. contraction, but differs in the more regularly elliptic semicells. It is scarcely to be separated from it. Var. ellipsoideum (Elfv.) West & G. S. West. (PI. LXI, figs. 28, 35.) Cosmarium ellipsoideum Elfv. Anteck. Finska Desm. 1881, p. 13, t. 1,'f. 10; De Toni, Syll. Alg. 1889, p. 953 ; West & G. S. West, Alg. S. England, 1897, p. 491. Ursinella ellipsoidea Kuntze, Revis. gen. plant. 1891, p. 924. Cosmarium contraction Kirchii. var. ellipsoideum (Elfv.) West & G. S. West, Alg. N. Ireland, 1902, p. 40. Cells shorter, not more than 1J times as long as broad, semicells more exactly elliptic, although the apex is sometimes slightly flattened in the middle. Cell-wall usually smooth. Zygospore globose and smooth. Length 31-51 //, ; breadth 24-42 ^ ; breadth of isthmus 7-12/x; thickness 14* 5-2 7 JJL; diam. zygosp. 29-36 p.. ENGLAND.- -Thursley Common, Surrey ! W AL K s .- -C ap el C urig, C am arvon shire ! SCOTLAND.- -Skye, and also plankton of Loch Bair- ness, Inverness ! Plankton of Lochs Langabhat, an Tomain, and Stranabhat, Lewis, and of Lochs COSMARIUM. 173 Diracleet and a Mhorgliain, Harris, Outer Hebrides ! Plankton of Loch Beosetter, Bressay, Shetlands ! IRELAND. — Small lakes between Clifden and Round- stone, Galway ! Geoc/r. Distribution.- -QeTm&ny. Sweden. Finland. N". Russia. Faeroes. Iceland. Australia. We do not think that C. ellipsoideum Elfv. differs sufficiently from C. contraction Kirchn. to warrant its separation as a distinct species, and we have therefore placed it as a variety of that species. It differs from typical C. contractum in having relatively shorter cells, with a less widely-open sinus, and more exactly elliptical semicells. It is very variable in size, and there are three forms worthy of special mention : (1) A form about half the normal size ; length 22— 23*5 ju; breadth 18-20 ju ; breadth of isthmus 6'5-7'6/u; thickness 11-12 /u. (PL LXI, figs. 30-32.) Not uncommon in the Scottish plankton. This form is probably identical with C. minutum Delp. ('Desm. subalp/ 1877, p. 105 (sep.), t. 7, f . 37-39) , and perhaps would be better placed as C. contractum var. minutum (Delp.). (2) A form of very variable size, with the sinus more closed (= C. ellipsoideum Elfv. var. minor Racib. Nonn. Desm. Polon. 1885, p. 84, t. 10, f. 9; C. proteiforme Turn. Freshw. Alg. E. India, 1893, p. 64, t. 9, f. 26); length 16-42 /u; breadth 11-29 ju ; breadth of isthmus 4-8 /u ; thickness 8-16 /u. (PL LXI, fig. 33). This form we have observed from Thursley Common, Surrey. (3) A form in which the cells are slightly retuse in the middle of each apex; cell-wall delicately punctate; length 32 /«; breadth 27'5ju; breadth of isthmus 5'5 /u (PI. LXI, fig. 29). This form we described and figured in f Alg. N. Ireland/ 1902, p. 40, t. 2. f. 10. It might stand as " var. ellipsoideum forma retusa" It was found at Grlenties and in Lough Anna, Donegal. Var. Gartanense West & G. S. West. (PL LXI, fig. 27.) C. contractum Kirchn. var. Gartanense West & G-. S. "West, Alg. X. Ireland, 1902, p. 41, t. 2, f. 9. Cells larger and usually a little longer ; semicells o «/ at the middle of the apex abruptly retuse-emarginate. Length 68 //, ; breadth 43-44 p. ; breadth of isthmus 10 p.. IEELAXD. — Lousfli Gartan, Donegal ! 174 BRITISH DESMID1ACEJS. Var. Cracoviense Racib. G. contractum Kirchn. e. Cracoviense Racib. Nonn. Desm. Polon. 1885, p. 84, t. 10, f. 10 ; Roy & Biss. Scott. Desm. 1894, p. 44. Semicells obtrapezoid, sides divergent and almost straight, basal and upper angles rounded, apex slightly convex. Length 31-34 /,; breadth 22-26 /i; breadth of isthmus 8-9 ju; thickness 16*5-19 /n. SCOTLAND. — Dinnet, Aberdeen (Roy fy Bissetf). 29. Cosmarium subcontractum West & G. S. West. (PL LXI, figs. 36, 37.) Cosmarium subcontractum'Wesb and G. S. West, Further Contrib. Freshw. Plankton Scott. Lochs, 1905, p. 484 [name only] ; Freshw. Alg. Ork- neys and Shetlands, 1905, p. 20, t. 1, f. 21. Cells small, a little longer than broad, very deeply constricted, sinus narrow near the apex but widely open outwards ; semicells obversely semicircular, with a broad and almost straight apex, upper lateral angles rounded ; side view of semicell circular. Vertical view elliptic, ratio of axes about 1 : 1*7. Cell-wall minutely punctate. Chloroplasts axile with one central pyrenoid. Zygospore unknown. Length 32- 5-34 /LI; breadth 30-31*5 ^; breadth of isthmus 7-8*5 /^; thickness 15-15*5 p. SCOTLAND.- -Bressay, Shetlands ! This species stands nearest to C. contractum Kirchn.,, but is distinguished by its broad, truncate apex. This feature c'auses the cells to be proportionately shorter. 30. Cosmarium subaversum Borge. (PI. LXI, fig. 38.) Cosmarium subaversum Borge, Algologiska Notiser, 1897, p. 211, t. 3, f . 1. Cells small, about 1^ times longer than broad, moderately constricted, sinus open and subrectangular ; semicells obsemicircular, upper angles well rounded, COSMAKIUM. 175 apex slightly convex. Side view of semicell subcir- cular. Vertical view broadly elliptic, ratio of axes about 1 : 1*2. Cell- wall smooth. Zygospore unknown. Length 24*5-26 p,; breadth 18-19*5 p.; breadth of isthmus 9 p. SCOTLAND.- -Mull in Argyll ; in plankton (Borge). C. subaversum Borge should be compared with C. aversum AVest & G. S. West, a species described from Madagascar. It is distinguished from that species by its much broader isthmus, by the more convex apices of the semicells, and by the elliptical vertical view. The cell-wall also is smooth, whereas that of C. aversum is irregularly punctate. 31. Cosmarium tetrachondrum Lund. (PI. LXII, fig. 1.) Cosmarium tetrachondrum Lund. Desm. Suec. 1871, p. 38, t. 3, f . 2 ; Nordst. Xorges Desm. 1873, p. 17 ; Jacobs. Desm. Danem. 1876, p. 195 ; Cooke, Brit. Desm. 1886, p. 89, t. 37, f . 5 ; De Toni, Syll. Alg. 1889, p. 956 ; Eoy & Biss. Scott. Desm. 1894, p. 176 ; Nordst. Index Desm. 1896, p. 253 ; West and G-. S. West, Alg. N. Ireland, 1902, p. 33. Ursinella trachondra Kuiitze, Revis. gen. plant. 1891, p. 925. Cells small, about 1^ times as broad as long, very deeply constricted, sinus very narrow and linear ; semicells transversely semi-elliptic (or very clepressed- subsemicircular), basal angles rounded, apex truncate- convex, with a granule just above and near the extremity of each linear sinus. Side view of semicell e/ circular with a basal granule on each side. Vertical view elliptic, ratio of axes about 1 : 2'25, with two granules on each side rather far apart. Cell-wall smooth. Chloroplasts axile, with only one pyrenoid. Zygospore globose and smooth, sometimes showing a tendency to elongate irregularly. Length 2O5 /^; breadth 23-26*3 p,; breadth of isth- mus 6-7 p.; thickness 1O7 p.. ENGLAND.- -Near Chapel Wood, S.E. Surrey ! SCOTLAND.- -Ross, Banff, Aberdeen, Kincardine, For- far, and Perth ; near Kingshouse, Argyll ; zygospores from Deeside, Aberdeen (Roy $• Bissett). 176 BRITISH DESMIDIACE^:. IRELAND. — Lough G-artan, Donegal ! Tipperary (Archer) . Geogr. Distribution. — Gralicia in Austria. Poland. S. Russia. Norway. Sweden. Denmark. 32. Cosmarium depression (Nag.) Lund. (PI. LXII, figs. 2-5.) Euastrum (Tetracanthium) depressum Nag. Gatt. Einzell. Alg. 1849, p. 114, t. 7 C, f. 2. Cosmarium depressum (Nag.) Lund. Desni. Suec. 1871, p. 38 ; Kirchn. Alg. Schles. 1878, p. 148 ; Wolle Desm. U. S. 1884, p. 64, t. 50, f . 10-12 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 195 ; De Toni, Syll. Alg. 1889, p. 940 ; Roy & Biss. Scott. Desm. 1894, p. 45 ; Nordst. Index Desm. 1896, p. 101 ; West & G. S. West, Freshw. Alg. Orkneys and Shetlands, 1905, p. 20. Staurastrum convergens (Ehrenb.) Menegh. (3 inermis Jacobs. Desm. Daneni. 1876, p. 203. Cosmarium Scenedesmus Delp. Desm. subalp. 1877, p. 5, t. 7, f . 28-34 ; Wolle, Desm. U. S. 1884, p. 59, t. 50, f . 7-9 ; De Toni, Syll. Alg. 1889, p. 956 ; West, Alg. N. Wales, 1890, p. 288 ; Add. Alg. W. Yorks. 1891, p. 246 ; Alg. W. Ireland, 1892, p. 145 ; Alg. Eng. Lake Distr. 1892, p. 725 ; Nordst. Index Desm. 1896, p. 229 ; West & G. S. West, Alg. S. England, 1897, p. 486 ; Alga-fl. Yorks. 1900, p. 73 ; Alg. N. Ireland, 1902, p. 33 ; Scott. Freshw. Plankton, I, 1903, p. 526. Ursinella depressa Kuntze, Eevis. gen. plant. 1891, p. 924. U. Scenedesmus Kuntze, 1. c. p. 925. Cosmarium Scenedesmus Delp. forma punctata West, Alg. W. Ireland. 1892, p. 145 ; Turner, Freshw. Alg. E. India, 1893, p. 60, t. 8, f. 61 [" (3 punctat um "] . Cells rather small, a little broader than long, deeply constricted, sinus narrowly linear, opening outwards ; semicells depressed, transversely subelliptic, apex con- vex-truncate, sides of semicells rounded. Side view of semicell circular. Vertical view elliptic, ratio of axes about 1 : 2*2. Cell-wall finely punctulate. Chloro- plasts axile, each with one pyrenoid. Zygospore globose or ellipsoid, smooth. Length 3 7-43 ^ ; breadth 40-50 ju ; breadth of isth- mus 12-14 u; thickness 17*5-20^; diam. zygosp. about 35 /u. ENGLAND. — Malham Tarn, AY. Yorks! Skip with Common, E. Yorks ! Epping Forest, Essex ! Thursley Common, Surrey ! AArALES.--Capel Curig, Llyn Idwal, and Llyn Ogwen, Carnarvonshire ! COSMARIUM. 177 SCOTLAND .- -Sutherland ! , Ross, Inverness!, Aber- deen, Perth ! (Roy §• Bissetf). Lewis and Harris, Outer Hebrides ! Orkneys ! Shetlands ! Not uncommon in the plankton ! IRELAND.- -Donegal ! Mayo ! Galway ! Kerry ! Dub- lin and Wicklow (Archer). Londonderry ! Geor/r. Distribution.- -Grermsinj. Galicia in Austria. Italy. Faeroes. Greenland. India. Ceylon. Burmah. New Zealand (var.). Australia. Abyssinia. United States. There appears to be no doubt of the almost strict identity of " Euastrum depression Nag." (1849) and "Cosmarium Scenedesmus Delp." (1877). Lundell first pointed out the affinities of this Desmid, and also placed it under the genus Cosmarium as C. depressum Nag. (Lund.). C. depressum is distinguished from C. Plutseolus by its proportionately greater breadth, by its depressed- elliptic semicells (not reniform), and by the absence of a central protuberance. It also bears a great resemblance to Arthro- desmus convergens Ehrenb. without the spines, and Jacobsen actually referred it to this species as "var. inermis." Var. achondrum (Boldt) West & G. S. West. (PI. LXII, figs. 6-9.) C. Phaseolus Breb. var. achondrum Boldt, Sibir. Chloropliy. 1885, p. 103, t. 5, f . 7 ; De Toni, Syll. Alg. 1889, p. 1002 ; Sclimidle, Beitr. Algenfl. Sch-warzwald. n. Rheineb. 1893, p. 102, t. 5, f. 11 ; Berg. FresliAv. Alg. OstgrSnl. 1894, p. 19, t, 1, f. 13 ; Roy & Biss. Scott. Desm. 1894, p. 171. C. depressum (Nag.) Lund. var. achondrum (Boldt) West & Gr. S. West. Further Contrib. Freslrvv. Plankton Scott. Lochs, 1905, p. 484. Cells as long as broad, or nearly so ; semicells sub- hexagonal-elliptic, apex broader and more truncate. Length 37-51 A*; breadth 40-51 /m ; breadth of isth- mus 12-17 /« ; thickness 22-23 p. EXGLAXD. — Malham Tarn, W. Yorks ! WALES.- -Capel Curig Lakes, Carnarvonshire! SCOTLAND.- -Near Loch Coruisk in Skye, Inverness (Roy ft Bissetf). Mull in Argyll (Borge). General in the plankton of the mainland and the Outer Hebrides ! IEELAXD.- -Lough Gartan, Donegal ! Lakes between Clif den and Roundstone, Gal way ! VOL. II. 12 178 BRITISH DESMIDIACEJ:. Geogr. Distribution. — Germany . G-alicia in Austria. Norway. Sweden. Bornliolm. Finland. Faeroes. Iceland. Spitzbergen. Uruguay. There are two very strong reasons for referring- this variety to C. depressum (Nag.) Lniid. rather than to C. PJiaseolus Breb. In the first place, there is an entire absence of the central protuberance which is a characteristic feature of all forms of C. PJiaseolus ; secondly, it is associated in large numbers with numerous specimens of C. depressum in the plankton of many of the lakes of the British Islands. Numer- ous intermediate forms occur in the plankton which clearly connect it with the more rounded typical forms of C. depressum. It is very variable in size and also in the width of its isthmus. Var. reniforme var. nov. (PL LXII, fig. 10.) Cells rather small; semicells narrowly reniform, sinus slightly open. Length 21 fj. ; breadth 26 /n ; breadth of isthmus 6-5,/. ' ENGLAND. — Helvellyn, Westmoreland ! This variety differs from (7. subdepressum West & Gr. S. West in the open sinus, the smooth cell-wall, and the presence of only one pyrenoid in each semicell. 83. Cosmarium subquadrans sp. nov. (PI. LXII, figs. 11-13.) Cells small, a little broader than long, oblong- quadrate, very deeply constricted, sinus very narrowly linear, slightly dilated at the extremity; semicells transversely oblong, basal angles obtuse, sides almost parallel in the lower half, upper half well rounded to form the upper angles, apex broad and truncate (slightly convex). Side view of semicell circular. Vertical view fusiform elliptic, ratio of axes about 1 : 2*14. Cell-wall smooth. Chloroplasts axile, each with two pyrenoids. Zygospore unknown. . 179 Length 21-5-25 p. ; breadth 26-5-30 /i; breadth of isthmus 6'5-Svft; thickness 14 ^. ENGLAND.- -Xear Bowness, Westmoreland ! IRELAND. --Small lakes between Clifden and Round- stone, Gal way ! This species comes near to C. quadrans Turn., but differs in being less quadrate,, in its proportionately greater breadth, in the more rounded upper angles of the semicells, and con- sequently in the much shorter sides. The cell-wall also is smooth. It should also be compared with C. subdepressum West & G. S. West ('Some N. Amer. Desm/ 1896, p. 247, t. 15, f. 15), from which it is distinguished by the angular form of its semicells, by the stouter vertical view, and by the smooth cell-wall. 34. Cosmarium succisum West. (PI. LXII, figs. 14-16.) Cosmarium succisum West, Alg. W. Ireland, 1892, p. 146, t. 20, f. 22, 23; Nordst. Index Desrn. 1896, p. 248 ; West & G. S. West, Alg. S. England, 1897, p. 486 ; Alga-fl. Yorks. 1900, p. 91. C. tinctum Ealfs var. succisum West &• G. S. West, Alg. X. Ireland, 1902, p. 34. Cells minute, about as long as broad, moderately constricted, sinus open, with a short, narrow ex- tremity ; semicells trapeziform-elliptic, angles rounded, sides slightly retuse, apex broadly truncate (or very slightly concave). Side view of semicell circular. Vertical view elliptic, very slightly subtumid at the middle on each side. Cell- wall smooth and of a yellow t/ or reddish-brown colour. Chloroplasts axile with one pyrenoid. Zygospore unknown. Length 1 0-12-5 /x,; breadth ll-12'o p,; breadth of isthmus 3*75-5 //,; thickness 6 (JL. ENGLAND. — Wigton Moor, W. Yorks ! Riccall and Skipwith Commons, E. Yorks ! Puttenham Common, Surrey ! WALES. — Capel Curig, Carnarvonshire ! IRELAND.- -Near Glenties and Lough Anna, Donegal ! Creggan and Derryclare Loughs, and Clifden, Galway ! 180 BRITISH DESMIDIACE^l. Lough Deryadd, Armagh ! Slieve Donarcl and Slieve Bearnagh, Down ! This species is distinguished at once from C. tinctum Ralfs by the form of its semicells both in the front and the vertical view. It differs from C. abbreviatum Eacib. in its smaller size, its different sinus, its relatively greater length, in the form of its semicells, the slight central protuberance of the vertical view, and the colour of its cell-wall. From C. pseudobiremum Boldt, it is distinguished by the form of its semicells, having the apex more truncate, by the less tumid vertical view, by its smaller size, and by the reddish-brown cell-wall. • 35. Cosmarium subretusiforme West & GL S. West. (PL LXII, fig. 19.) Cosmarium subretusiforme West & Gr. S. West, New Brit. Freshw. Alg. 1894, p. 5, t. 1, f. 20 ; Nordst. Index Desm. 1896, p. 247. Cells very minute, 1J times longer than broad, moderately constricted, sinus open and obtuse ; semi- cells subrectaiigular, basal angles broadly rounded, upper part of sides retuse, upper angles acute, apex broadly truncate and straight. Side view of semicell elliptic- subcircular. Vertical view elliptic with sub- acute poles, ratio of axes about 1 : 2'2. Cell- wall smooth. Z ygospore unknown . Length 7'S-8ju; breadth 6'2-6'5/x,; breadth of apex 5*5 ju, ; breadth of isthmus 4*5 JJL ; thickness o JJL. ENGLAND.- -Borrowdale, Cumberland ! This minute species approaches Cosmarium retusiforme (\Ville) Gutw. in its front view, but is distinguished by its much smaller size, its broader apices, and its different side and vertical views. 36. Cosmarium retusiforme (Wille) Gutw. (PL LXII, figs. 17, 18.) Cosmarium Hammeri Eeinsch var. retusiforme Wille, Norges Ferskv. Alg. 1880, p. 32, t. 1, f . 16. C. retusiforme (Wille) Gutw. Wahr. d. Prioritat, 1890, p. 69; Flor. Glon. Okolic Lwowa, 1891, p. 55, t. 2, f. 12. COSMARIUM. 181 Cells small, a little longer than broad, deeply con- stricted, sinus narrow, opening outwards ; semicells truncate-subpyramidate, lower half of sides rounded, upper half markedly retuse, apex widely truncate and straight, upper angles sharp and rectangular. Side view of semicell ovate, upper part of sides retuse. Vertical view elliptic, inflated at the middle on each side. Cell- wall smooth. Chloroplasts axile, with one pyrenoid. Zy go spore unknown. Length 22'5-24/x; breadth 19-19-5 JA; breadth of isthmus 6-7 ^; breadth of apex 9-1 2 /x; thickness 12-13 p,. IRELAND. — Ballynahinch, Galway ! Geof/r. Distribution. — Austria (var.) and Galicia. Poland. Central Africa. United States. Brazil (var.). This species hears some resemblance to C. retumm (Perty) Rabenh., but the latter is larger,, more deeply constricted, with a more produced apical part of the semicells, which is not so wide, and is also sparsely furnished with granules. C. retusifonne differs from C. Hammeri in its more open sinus, its abruptly-truncate apex, its sharp superior angles, and in its smaller size. 37. Cosmarium Hammeri Reinsch. (PL LXII, figs. 20, 21.) Cosmarium Hammeri Eeinsch, Spec. Gen. Alg. 1867, p. 115, t. 22 B, I, f. 1-10 [inclusive of A. majus and B. intermedium^ ; Lund. Desm. Suec. 1871, p. 37 ; Wolle, Desm. U. S. 1884, p. 79, t. 18, f. 27 ; Cooke, Brit. Desm. 1886, p. 81 ; Hansgirg, Prodr. Algenfl. Bohm. 1888, p. 194; De Toni, Syll. Alg. 1889, p. 936 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, p. 142; Alg. Eng. Lake Distr. 1892, p. 724; Eoy & Biss. Scott. Desm. 1894, p. 103 ; West & G. S. West, Some N. Amer. Desm. 1896, p. 245 ; Norclst. Index Desm. 1896, p. 137 ; West & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 74 ; Alg. N. Ireland, 1902, p. 32. Didymidium (Cosmarium) Hammeri A. majus Eeinsch, Algenfl. Frank. 1867, p. Ill, t. 10, f. 1. Euastrum Hammeri Cohn, Desm. Bong. 1879, p. 270. Ursinella Hammeri Kuntze, Eevis. gen. plant. 1891, p. 924. Cells of moderate size, about 1 J times longer than broad, subhexagonal, deeply constricted, sinus narrowly linear with a dilated apex, opening outwards ; semi- cells truncate-pyramidate, basal angles well rounded, 182 BRITISH DESMIDIACE.E. upper part of sides suddenly converging and slightly retuse, upper angles rounded, apex broadly truncate, straight or slightly retuse. Side view of semicell elliptic-ovate. Vertical view elliptic, ratio of axes about 1 : 1'8. Cell-wall smooth. Chloroplasts axile with one pyrenoid. Zygospore unknown. Length 40-50 p ; breadth 27-35 //, ; breadth of isthmus 11-13 ^; EXGLAXD. — Westmoreland! (Bissett). T\r. Yorks. WALES.- -Xear Bodorgan, Anglesey ! SCOTLAND.- -Xear Rhiconich, Sutherland ! lEELAND.--Gralway ! Dublin and Wicklow (Arclier.) Geogr. Distribution. — France. Germany. Galicia in Austria. Hungary. Italy. Portugal. Norway. Sweden. Denmark. X. and S. Russia. Finland. Siberia. Greenland. Central China. Japan. India. Ceylon. Burmah. Sumatra (form). New Zealand (var.). Australia. Central and E. Africa. United States. Brazil. Paraguay. Patagonia. Despite its world-wide distribution the form of C. Hammeri described by Reinsch as " A. majns ' ' is a very rare British Desmid. This form we regard as the type of the species,, and it possesses an elliptical vertical view with no trace of a median inflation. Var. homalodermum (Xorclst.) nob. (PI. LXII, figs. 22, 23.) Cosmarium pyramidatum Breb. forma intermedia Nordst. ~N"orges Desm. 1873, p. 19. Cosmarium homalodermum Nordst. Desm. Arctoee, 1875, p. 18, t. 6, f . 4 ; Desm. Ital. 1876, p. 34 ; Wolle, Desm. U. S. 1884, p. 81, t. 17, f . 19, 20 ; Cooke, Brit. Desm. 1886, p. 82, t. 36, f. 7 ; De Toni, Syll. Algar. 1889, p. 1043 ; West, Alg. N". Yorks. 1889, p. 292 ; Alg. N. Wales, 1890, p. 288 ; Eoy & Biss. Scott. Desiii. 1894, p. 104 ; Norclst. Index Desm. 1896, p. 141. C. homalodermum Rordst. var. rotunClatum'WilLe, Ferskv. Alg. N"ov. Semlja, 1879, p. 36, t. 12, f . 18. Ursinella homaloderma Kuntze, E,evis. gen. plant. 1891, p. 924. Cells rather larger, sometimes shorter ; vertical view slio'htlv tumid at the middle on each side : side view ti of semicell more ovate (sometimes subspherical) ; cell- wall thicker, very finely and often indistinctly punctate. COSMARIUM. 183 Length 54-00 /x : breadth 48-51 ^ ; breadth of apex about 19-20/u; breadth of isthmus 18-19/x; thickness 29-34 /x. ENGLAND.- -Westmoreland ! W., JST., and E. Yorks ! Devon (Bennett). Cornwall! (Marquand). WALES.- -Moel Siabod, Snowdon, and Yr Orsedd, Carnarvonshire ! Dolgelly, Merioneth ! SCOTLAND.- -Ross, Inverness, Aberdeen, Kincardine, Forfar !, Perth, Stirling, Argyll (Roy $' Bissett). Sutherland ! Orkneys ! IRELAND.- -Donegal ! Galway ! Kerry! Geoc/r. Distribution. — Germany. Norway. Sweden. Greenland. Spitsbergen. Nova Zembla. N. Russia. Faeroes. India. This variety differs principally from C. Hammeri in its larger size and in the tumid vertical view. It is, however, very variable, especially with, regard to the sides of the semicells and the apex. The latter may he slightly retuse, straight, or convex,, and the apices of the semicells of one individual may differ considerably. In Britain it is found mostly in subalpine localities, especially in mountain springs and in the vicinity of dripping rocks. We have included in this variety " C. homalodermum var. rotundafum Wille ;' as the side view of the semicell is some- what variable. Intermediate stages can be met with between a subcircular and an ovate side view. Borgesen also finds this D eg mid to be very variable in the Faeroes, and to reach a leno-th of 70^ and a breadth of 58 /u (vide 'Freshw. Alg. Faeroes/ 1901, p. 222). Var. protuberans West & G. S. West. (PI. LXII, figs. 24, 25.) C. Hammeri Eeinsch. var. "with inflated sides" Wolle, Desm. U.S. 1884, t, 18, f . 36-38. C. Hammeri Eeinsch var. protuberans West and G. S. West, Some N". Amer. Desm. 1896, p. 246, t. 14, f. 35. Cells rather small; vertical view with a median tumour on each side. Zygospore globose, furnished with numerous, simple spines, which are dilated at the base. 184 BRITISH DESMIDIACE-3E. Length 24-35 ju; breadth 18'5-21'5ju; breadth of isthmus 7-7*5 ju ; thickness H-12'5//,; diam. zygosp. without spines 30 /i, with spines 46 /x. SCOTLAND. — Harris, Outer Hebrides ! Geogr. Distribution. — United States. In the zygospore we examined (from the United States) the apices of the spines were simple, but Wolle has figured a zygospore in which the spines are furcate. Var. Hibernicum Cooke. C. Hammeri forma, Crowe in Quart. Journ. Micr. Sci. 1873, p. 435. C. Hammeri var. Hibernicum Cooke, Brit. Desm. 1886, p. 81. Cells about 1^- times longer than broad, apices convex-truncate ; in the side view with a minute tooth- like protuberance visible at the constriction. IRELAND. — Arklow, Co. Wicklow (Crowe). 38. Cosmarium Nymannianum Grim. (PI. LXII, figs. 26, 27.) Cosmarium Nymannianum Grim, in Rabeiih. Flor. Europ. Alg. Ill, 1868, p. 166 ; Lund Desm. Suec. 1871, p. 36, t. 3, f. 1 ; Wolle, Desm. U. S. 1884, p. 79 ; Cooke, Brit. Desm. 1886, p. 82, t. 36, f . 1 ; De Toiii, Syll. Alg. 1889, p. 964 ; West, Alg. W. Ireland, 1892, p. 142 ; Alg. Eng. Lake Distr. 1892, p. 724 ; Roy & Biss. Scott. Desm. 1894, p. 169 ; Nordst. Index Desm. 1896, p. 184 ; West & O. S. West, Alg. S. England, 1897, p. 485; Alga-fl. Yorks. 1900, p. 78; Alg. N. Ireland, 1902, p. 32; Freshw. Alg. Ceylon, 1902, p. 161. Ursinella Nymanniana Kiintze, Eevis. gen. plant. 1891, p. 925. Cells rather small, elongate-subhexagonal, about 1-J times longer than broad, deeply constricted, sinus narrowly linear with a dilated extremity; semicells truncate-pyramidate, basal angles rounded, lower half of sides convex, upper half concave, upper angles rounded, apex retuse, in the centre with a large and conspicuous scrobiculation. Side view of semicell subcircular. Vertical view subrhomboid-elliptic, at the middle on each side thickened and showing the large scrobiculation, ratio of axes about 1 : 1*8. Cell-wall distinctly punctate. Chloroplasts axile, each with one pyrenoid. Zygospore unknown. COSMARIUM. 185 Length. 44-48^; breadth 33-3// $* 7>/*.sr/f). Near Lerwick, Shet- land s ! IRELAND.- -Lough Anna and Sproule's Lough, Done- gal ! Ballynahinch, and Loughs Creggan, Derryclare, Letereen, and Shannacloontippen, Gralway ! Adrigole, Kerry ! Lough Derryadd, Armagh ! Geoyr. Distribution.- -Germany. G-alicia in Austria. Norway. Japan (var.). W. Africa. United States. Brazil. Argentina. ~ C. gcdfritum somewhat resembles C.Lundelliivar. ellipticum, but the semieells are mere pyramidate, the poles of the vertical view are not so pointed, and in size it is a little smaller. It is a Cosmarium which in the British Islands is constantly associated with C. tetragonnm, C. speciosum, C. notabile, C. ocJithodes, and other upland species. 45. Cosmarium pseudonitidulum Nordst. (PL LXIII, fig. 26.) Cosmarium pseudonitidulum Nordst. Norges Desm. 1873, p. 16, t. 1, f . 4 ; Wolle, Desm. U.S. 1884, p. 62, t. 18, f. 19 ; Cooke, Brit. Desm. 1886, p. 87, t. 42, f . 15 [figures bad] ; De Toni, Syll. Alg. 1889, p. 973 ; West, Alg. N. Wales, 1890, p. 288 ; Alg. W. Ireland, 1892, p. 145 ; Eoy & Biss. Scott. Desm. 1894, p 172 ; Nordst. Index Desm. 1896, p. 209 ; West & G. S. West, Alga-n. Yorks. 1900, p. 78. Ursinella pseudonitidula Kuntze, Revis. gen. plant. 1891, p. 925. Cells of moderate size, truncate-elliptic, about 1J times longer than broad, deeply constricted, sinus narrowly linear with a dilated extremity ; semieells snbtrapezoid or triincate-pyramidate, basal angles rounded, sides convex, at first suberect and then gradually converging, upper angles rounded, apex broadly truncate and very slightly convex. Side view of semicell ovate-circular. Vertical view elliptic, ratio of axes about 1 : 1/6. Cell- wall punctate. Chloro- plasts axile, each with two pyrenoids. Zygospore unknown. 196 BTUTTSH DESMTDIACE^. Length 42 p, ; breadth 33 ^ ; breadth of isthmus IG/i; thickness 17-18 JJL. ENGLAND.- -Bowness, Westmoreland ! Cullingworth, W. Yorks ! Mickle Fell, N. Yorks ! WALES.- -Bettws-y-coed !, Capel Curig ! (Coolie $• Wills), Snowdon (Roy), and Yr Orsedd !, Carnarvon- shire. SCOTLAND. — Orkneys!, Sutherland, Ross, Inverness, Aberdeen, Kincardine, Forfar, Perth, Argyll, Arran (Roy $ Bissett). IRELAND.- -Adrigole, Kerry ! Geogr. Distribution.- -Norway. Poland. Siam. Cen- tral China. United States. This species stands very near to C. nitidulum De Not., but differs in the form of the semicells, which are wider at the apex, and in the presence of two pyrenoids in each chloro- plast. From C. galeritum Nordst. it is distinguished by its smaller size and by its less pyramidate semicells with broader apices. Var. validum nob. (PL LXIII, figs. 27-30.) C. pachydermum Lund. var. minus Nordst. Norges. Desm. 1873, p. IS, t. 1, f . 7 ; De Toni, Syll. Alg. 1889, p. 970 ; Roy & Biss. Scott. Desm. 1894, p. 170 ; West & G. S. West, Desm. Singapore, 1897, p. 164 ; Fresh w. Alg. Ceylon, 1902, p. 162. Cells larger than in the type, with the basal angles sometimes more rectangular (not so rounded) ; cell- wall very firm and punctate. Length 56-78 p. ; breadth 46-59 p. ; breadth of isth- mus 17-25 //,; thickness 28— 33 /A. ENGLAND.- -Near Bowness, Westmoreland (Bissett). Cautley Spout, W. Yorks ! WALES. — Capel Curig, Carnarvonshire ! SCOTLAND.- -Poolewe, Ross ; near Brin, Inverness ; Glen Callater, Aberdeen ; Canlochan, Forfar ; Bannock, Perth; Alva Glen, Stirling (Roy fy Bissett). Geocjr. Distribution.- -Norway. India. Ceylon. Singapore. Azores. W. Africa. This variety only differs from typical C. pseudonitidulum in its larger size and sometimes in its more rectangular basal rOSMAIHUM. 197 angles. The latter may even be slightly produced as in fig. 28, PL LXIII. Although originally described as a variety of C. pachydermum, we do not think it has any close nflinity with that species, the outward form of the semicells 1 icing so very different. 46. Cosmarium nitidulum De Not. (PL LXIV, figs. 1-3.) Cosmarium nitidulum De Not. Desm. Ital. 1867, p. 42, t. 3, f. 26 ; Rabenh. Flor. Em-op. Algar. Ill, 1868, p. 169; Lund. Desm. Suec. 1871, p. 35; Wolle, Desm. U.S. 1884, p. 62, t. 18, f . 18, t. 52, f. 9-10 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 194 ; Nordst. Preshw. Alg. N. Zeal. 1888, p. 59, t. 6, f. 17 ; De Toni, Syll. Alg. 1889, p. 935 ; West, Alg. N. Wales, 1890, p. 288 ; Alg-. W. Ireland, 1892, p. 145 ; Alg. Eng. Lake Distr. 1892, p. 725 ; Roy & Biss. Scott. Desm. 1894, p. 169 ; Nordst. Index Desm. 1896, p. 181 ; West & G. S. West, Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 78. Euastrum (Cosmarium) nitidulum Gay forma genuina Gay, Monogr. loc. Conj. 1884, p. 59. Cosmarium nitidulum De Not. f. punctulata Gutw. Flor. glon. Galic. 2, 1890, p. 14, t. 1, f. 11. Ursinella nitidula Kuntze, Eevis. gen. plant. 1891, p. 925. ? Cosmarium rectosporum Turn. Freshw. Alg. E. India, 1893, p. 69, t. 10, f. 16. Cells of moderate size, a little longer than broad, deeply constricted, sinus very narrowly linear with a slightly-dilated extremity ; semicells truncate-subsemi- circular, basal angles broadly rounded, sides convex and converging upwards, upper angles slightly rounded, apex small, truncate-convex, straight, or slightly retuse. Side view of semicell subcircular. Vertical view elliptic. Cell-wall very minutely punctate (punctula- tions often scarcely visible). Chloroplasts axile, each with one pyrenoid. Zygospore unknown. Length 30-41 //, ; breadth 23-33 p, ; breadth of isthmus 8-10 /*, ; thickness 16-22 '5 p.. ENGLAND. — Cullingworth, W. Yorks ! Mickle Fell, Pilmoor, and near Bees Cliff, N. Yorks ! Leicester- shire (Roy). Thursley Common, Surrey! WALES. — Capel Curig (CooJce fy Wills') and Bethesda!, Carnarvonshire. SCOTLAND.- -Heughhead near Aboyne, and foot of 198 BRITISH DESMIDIACE^E. Culblean, Aberdeen ; N.W. side of Kerloch, Kincardine (Roy cj- Bissett). Meal Odhar, Perth ! IRELAND. — Lough Derryclare, Kylemore, and lakes between Clifden and Roundstone, Galway ! Lough Guitane and Sugar Loaf Mt., Kerry ! Geogr. Distribution. — France. Germany. Austria and Glalicia. Italy. Sweden. Finland. N. Russia. Central China. Japan. New Zealand. Australia. United States. W. Indies. Brazil. There is very little distinction between C. nitidulum and C. pseudonitidulum except for the difference in the pyrenoids. The semicells of C. nitidulum are generally more angular with a narrower apex and straighter sides. C. nitidulum and C. subtumidum are also very closely related, hnt the semicells of the latter are much more rounded, with broader basal angles, more convex sides, and a less angular apex. 47. Cosmarium canaliculatum West & G-. S. West. (PL LXIV, fig. 4.) Cosmarium canaliculatum West & G. S. West, New and Int. Freshw. Alg. 1896, p. 154, t. 4, f. 57 ; Alg. S. England, 1897, p. 485. Cells of medium size, about 1-g- times longer than broad, deeply constricted, sinus narrowly linear with a slightly-dilated extremity ; semicells truncate-pyrami- date, basal angles well rounded, sides almost straight or slightly convex, upper angles rounded, apex truncate and slightly convex. Side view of semicell shortly ovate towards the base with a slight swelling on each side. Vertical view elliptic, with a wide protuberance at the middle on each side. Cell-wall very thick, densely and irregularly scrobiculate, causing the exterior to appear slightly rough. Zygospore unknown. Length 72 ^ ; breadth 51 p ; breadth of isthmus 17*5 p, ; thickness 35 //,. ENGLAND.- -Near Goring, S.E. Oxfordshire! This species is rather smaller than the average examples of Cosmarium pyramidatum Breb., from which it is distinguished by the form of the front view, by its central protuberance, its COSMARIUM. 199 thicker cell-wall, and its more pronounced scrobiculations. Owing to the thickness of the cell-wall the latter have the appearance of short canals, and their large size and the comparative closeness of their disposition give the exterior of the cell-wall a slightly rough appearance. 48. Cosmarium pyramidatum Breb. (PL LXIV, figs. 5-7.) Cosmarium pyramidatum Breb. in Ralfs' Brit. Desni. 18-18, p. 94-, t. 15, f . 4 a-c ; Arch, in Pritch. Iiif us. 1861, p. 731, t. 3, f. 1-4, 15 (in part) ; Rabenh. Flor. Europ. Alg. Ill, 1868, p. 162; Lund. Desm. Suec. 1871, p. 41 ; Delp. Desm. Subalp. 1877, p. 33, t. 9, f. 30-33 ; Kirchn. Alg. Schles. 1878, p. 149 ; Wolle, Desm. U. S. 1884, p. 69, t. 14, f. 16 ; Cooke, Brit. Desm. 1886, p. 86, t. 36, f. 13; Hansg. Prodr. Algenfl. Bolim. 1888, p. 197 ; De Toni, Syll. Alg. 1889, p. 969 ; West, Alg. N. Yorks, 1889, p. 292 ; Alg. N. Wales, 1890, p. 288 ; Heimerl, Desm. alp. 1891, p. 596 ; West, Alg. W. Ireland, 1892, p. 144 ; Alg. Eiig. Lake District, 1892, p. 724 ; Eoy & Biss. Scott. Desm. 1894, p. 173 ; Nordst. Index Desm. 1896, p. 215 ; West & G. S. West, Welw. Afric. Freshw. Alg. 1897, p. 115 ; Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 78 ; Alg. N. Ireland, 1902, p. 33. Didymidium (Cosmarium) pyramidatum Reinsch, Algenfl. Frank, 1867, p. 107. Cosmarium pyramidatum b. typicum Klebs, Desm. Ostpreuss. 1879, 13. 31, t. 3, f. 18, 19, 31. Ursinella pyramidata Kuntze, Revis. gen. plant. 1891, p. 925. Cells large, about 1^ times as long as broad, truncate- elliptic in outline, deeply constricted, sinus very narrow and dilated towards the apex ; semicells truncate- pyramidate, basal angles well rounded, sides convex and in the upper part converging, upper angles obtuse, apex narrowly truncate. Side view of semicell elliptic oblong. Vertical view elliptic, ratio of axes about ] : 1'7. Cell- wall minutely scrobiculate. Chloroplasts axile, each with two pyrenoids. (Zygospore globose and tuberculated.) Length 58-100 /* ; breadth 45-62 p. ; breadth of isthmus 17'5-20//,; thickness 26*5-36 /x. ENGLAND.- -Cumberland ! Westmoreland! (Ralfs). AY., N., and E. Yorks ! Lancashire ! (Ralfs). Cheshire (Rolfs). Warwick (Wills). Surrey I (Ralfs). Sussex (Ralfs). Kent (Rolfs). Hants! (Bennett). Devon! (Bennett). Cornwall! (Ralfs). 200 BRITISH DESMIDIACE^:. WALES. — General in Carnarvonshire! Dolgelly, Merioneth (Ralfs). SCOTLAND.- -General ! (Roy fy Bissett). Common in the Outer Hebrides ! Orkneys ! Shetlands ! IRELAND. — Donegal ! Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Down ! Geogr. Distribution. — France. Germany. Austria and Galicia. Hungary. Italy. Norway. Sweden. Denmark. Bornholm. Finland. S. Russia. India. Ceylon. Burmah (form). "W. Africa. Azores. United States. Brazil. Paraguay. Uruguay (form). Argentina. Patagonia (form). C. pyramidatum is generally distributed in the peat-bogs and peaty pools of the British Islands. It is also abundant in the rocky pools and lakes of the western areas of Scotland and Ireland. Ralfs states that he obtained the zygospores at Dolgelly in Wales, but they do not appear to have been observed since. It is quite possible that the zygospores Ralfs examined were those of C. pseudopyramidatum, as that species was included in his C. pyramidatum. Moreover, he describes them as " tuberculated/' which is a conspicuous feature of the zygo- spores of C. pseudopyramidatum. The largest form of the species (forma tropica West & G. S. West) is known from Angola, W. Africa. It reaches a length of 170 /^ and a breadth of 90 /<, and the semicells are slightly inflated with less truncate apices. Var. angustatum West & G. S. West. (PI. LXIV, fig. 8.) C. pyramidatum Breb. var. anyustatum West & G. S. West, New Brit. Freshw. Alg. 1894, p. 5, t. 1, f. 18. Cells narrower than in the type, almost twice as long as broad ; semicells more evidently pyramidate, with straighter sides, basal angles very little rounded and almost submamillate. Length 90-92 p ; breadth 48-50 p. ; breadth of isth- mus 13 '5-1 5 p. ENGLAND. --Near Bowness, Westmoreland ! IRELAND. — Castletown, Kerry ! * •/ COSMAIUUM. 201 49. Cosmarium pseudopyramidatum Lund. (PL LXIV5 figs. 9-12.) Cosmarium pyramidatum Breb. in Ralfs' Brit. Desiii. 1848, p. 94, t. 15, f. 4d, e,f. " C. pyramidatum Breb. var. minus Eeinsch in Rabenh. Alg. 1868, no. 1902, f. 6. C. pseudopyramidatum Lund. Desm. Suec. 1871, p. 41, t. 2, f. 18; Nordst. Desm. Spetsb. 1872, p. 29 ; Wolle, Desm. U.S. 1884, p. 69, t. 15, f . 11-13, t, 16, f . 5, 6 ; Cooke, Brit. Desm. 1886, p. 86, t. 37, f . 2 ; Hansg. Prodr. Algenfl. Bohm. 1888, p. 198 ; De Toni, Syll. Alg. 1889, p. 946 ; West, Alg. N. Wales, 1889, p. 288 ; Heimerl, Desm. alp. 1891, p. 597 ; West, Alg. W. Ireland, 1892, p. 144 ; Alg. Eng. Lake Distr. 1892, p. 724 ; Eoy & Biss. Scott. Desm. 1894, p. 172; West & Of. S. West, Alg. Madag. 1895, p. 56 ; Some N. Amer. Desm. 1896, p. 246, t. 15, f . 2 ; Nordst. Index Desm. 1896, p. 210 ; West & Cr. S. West, Welw. Afric. Freshw. Alg. 1897, p. 115; Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 78 ; Alg. N. Ireland, 1902, p. 33. Euastrum (Cosmarium) pseudopyramidatum Gay, Monogr. loc. Conj. 1884, p. 60. Ursinella pseudopyramidata Kuntze, Revis. gen. plant. 1891, p. 925. Cells of moderate size, about If times as long as broad, deeply constricted, sinus narrowly linear ; semi- cells truncate-pyramidate or truncate-semi-elliptical, basal angles rounded, sides convex and converging to apex which is narrowly truncate, upper angles obtuse. Side view of semicell broadly elliptic. Vertical view elliptic, ratio of axes about 1 : 1*8. Cell- wall distinctly punctate. Chloroplasts axile, each with one pyrenoid. Zygospore globose or ellipsoid, furnished with scattered submamillate warts. Length 43-50 p.; breadth 25-33^; breadth of isthmus 7-10*5 /x ; thickness 17-19'5ju,; diam. zygosp. with warts 32-44 /x. ENGLAND. --Cumberland! Westmoreland ! (Bissett). W., N., and E. Yorks! Warwick (Wills). Surrey! Hants! (Bennett). Devon! Cornwall! (Marquand). WALES. — Near Bethesda ! , Capel Curig ! (CooJce § Wills), Grlyder Fawr ! , and Pen-y-gwryd (Roy), Carnarvonshire. Llyn Coron, Anglesey ! SCOTLAND. — Sutherland ! , Ross, Inverness ! , Aber- deen, Kincardine, Forf ar ! , Perth ! , Dumbarton, Argyll, Arran (Roy § Bissett). Stirling! Common in the Outer Hebrides ! VOL. ir. 14 202 BRITISH DESMlDIACE^l. IRELAND. — Donegal ! Mayo ! Galway ! Kerry ! Dublin and Wicklow (Archer). Down ! Geogr. Distribution. — France. Germany. Austria and Galicia. Poland. Hungary. Italy. Norway. Sweden. Finland. N. and S. Russia. Siberia. Spitz- bergen. Nova Zembla. Faeroes. Ceylon. Siam. New Zealand (var.). Australia. W., Central, and E. Africa. Madagascar. United States. W. Indies. Brazil. Paraguay. Uruguay. C.pseudopyramidatum is not so abundant as C. pyramidatum } from which it is distinguished by its much smaller size and by the presence of only one pyrenoid in the chloroplast of each semicell. Nordstedt's " forma minor " and " forma major," which he describes from Spitsbergen, we include within the general range of size for this species. Lundell also mentions a " forma major " • length 52-64 /a • breadth 32-40 /LL ; breadth of isthmus 11-15 ju. This he states to be identical with Ralfs' figs. 4 dj e, and /of C. pyramidatum. It is, however, difficult to fix an arbitrary range of size for a "forma major" and these dimensions should really be included with those given under the description of the species. Var. stenonotum Nordst. (PI. LXIV, fig. 13.) C. pseudopyramidatum Lund, stibsp. stenonotum Nordst. Desm. Ital. 1876, p. 32, t. 12, f . 8 ; De Toni, Syll. Alg. 1889, p. 946 ; Eoy & Biss. Scott. Desm. 1894, p. 172. C. pyramidatum Breb. c. stenonotum Klebs, Desm. Ostpreuss. 1879, p. 31, t. 3, f . 28-30. Cells mucb larger, upper part of semicells suddenly narrowed, lateral margins below the apex slightly retuse. With one pyrenoid in each chloroplast. Length 78-80 p; breadth 46-48 ^; breadth of isth- mus 16-1 7 p.; thickness 28-30 /x. WALES.- -Capel Curig and Glyder Fawr, Carnarvon- shire (Roy). SCOTLAND. — Poolewe, Ross ; Aberdeen ; Kincardine ; Ben Laoigh, Argyll (Roy $ Bissett). Geogr. Distribution.— -Norway. Sweden. Italy. Poland. N. Russia. Bornholm. Japan. Australia. W. Indies. Paraguay. 203 This variety differs from C. pyramidatum var. angustabum in the more rectangular basal angles of the semicells and the more protracted apices, as well as in the single pyrenoids. A small form of it is known from Australia and the West Indies: — length 35-36*5^; breadth 22-24 n ; breadth of isthmus 6*5-12 u thickness 50. Cosmarium variolatum Lund. (PL LXIV, figs. 14-16.) Cosmarium variolatum Lund. Desm. Suec. 1871, p. 41, t. 2, f. 19 ; Wolle, Desni. U. S. 1884, p. 63, t. 16, f . 3, 4 ; Cooke, Brit. Desm. 1886, p. 84, t. 36, f . 10 [figure bad] ; De Toni, Syll. Alg. 1889, p. 954 ; West, Alg. W. Ireland, 1892, p. 144 ; Alg. Eng. Lake Distr. 1892, p. 724 ; Eoy & Biss. Scott. Desm. 1894, p. 177 ; Nordst. Index Desni. 1896, p. 267 ; West & G. S. West, Welw. Afric. FresliAv. Alg. 1897, p. 115 ; Alg. S. England, 1897, p. 485 ; Alga-fl. Yorks. 1900, p. 78 ; Alg. N. Ireland, 1902, p. 33. C. pseudopyramidatum Lund. var. variolatum Hansg. Prodr. Algenfl. Bohm. 1888, p. 198. Ursinella variolata Kuntze, Revis. gen. plant. 1891, p. 926. Cells small, about If times longer than broad, deeply constricted, sinus narrowly linear witli a slightly-dilated apex ; semicells semi-elliptic, basal angles very slightly rounded, sides convex and upwardly converging, apex very narrow, truncate, and often subretuse. Side view of semicell obovate-elliptic. Vertical view broadly elliptic, ratio of axes about 1 : 1'S. Cell- wall firm, densely scrobiculate, the scrobiculations being rela- tively large and very conspicuous. Chloroplasts axile, each with one pyrenoid. Zygospore unknown. Length 32-35 /x; breadth 18-21 p.; breadth of isth- mus 5-6'5/>t; thickness 15-16*5 //,. ENGLAND. — Near Bowness, Westmoreland (Bissett). Baildon, W. Yorks ! Thursley Common, Surrey ! New Forest, Hants ! WALES. — Capel Curig, Carnarvonshire ! (Cooke §~ Wills). SCOTLAND. — Ross, Aberdeen, Kincardine, Perth, Argyll, Arran (Roy fy Bissett). Sutherland ! Outer Hebrides ! Orkneys ! IRELAND. — E. of Grlenties, Donegal ! Ballynahinch, 204 BEITISH DESMIDIACE^l. Lougli Athry, and lakes between Clifden and Round- stone, Galway ! Adrigole, Kerry ! Dublin and Wicklow (Archer). Geogr. Distribution. — Germany. Galicia in Austria, Poland (var.). Norway. Sweden. Ceylon. New Zealand (var.). Australia (var.). "W. Africa. United States. Brazil. This characteristic little species is easily distinguished from C. pseudopyramidatum by its smaller size and its densely- scrobiculate cell-wall. It is a much rarer .Desmid than either of the two preceding species. EXPLANATIONS OF THE PLATES ( 206 ) EXPLANATION OF THE LETTERING. a, «/. Front view of cell or semicell. h, It' . Vertical view. c. Side view. d. Basal view of semicell. Plate 33 PLATE XXXIII. FIGS. PAGE 1-3. — .Euastrum ventricosum Lund. All x 430 . 4 4-6. — E. crassum (Breb.) Kiitz. 4 and 6, x 430; 5, x 400. The upper semicell of fig. 6 shows a common variation in which there is a median rounded protuberance on the sides of the semi- cell . . . . .5 7-8. — E. crassum var. scrobiculatum Lund. All x 430 . 7 i ri . Plate 34 PLATE XXXIV. FIGS. PAGE 1-2. — Euastrum humerosum Ralfs. 1, x 520 ; 2, x 400 (after Ralfs) . . . .8 3-6.— E. pinnatum Ralfs. 3-5, x 430 ; 6, x 400 . 10 7-9.— E. oblongum (Grey.) Ralfs. All x 430. Fig. 8 is the side view and fig. 9 the vertical view taken from a smaller specimen than fig. 7 . 12 10. — E. oblongum var. depauperatumWest & G-. S. West. x 520 15 Plate 35 PLATE XXXV. FIGS. PAGK 1. — Euastrum oblongum (Grrev.) Ralfs var. cephalo- phorum West, x 400 . . .14 2. — E. oblongum. Zygospore, x 220 . . 14 Z-l.—E. Didelta (Turp.) Ralfs. 3, 5, and 6, x 430; 4, x 220; 7, zygospore, x 220 . 15 8-10. — E. ampullaceum Ralfs. 8 and 9, x 520 ; 10, zygospore, x 390 . . .19 11-12.— E. affine Ralfs. 11, x 400 (after Ralfs); 12. x 430 17 'XV. Plate 36 PLATE XXXYI. FIGS. PAGT5 1. — Euastrum sinuosum Lenorm. x 480 . 20 2-3. — E. sinuosum var. reductum West & G. S. West. 2, x 430; 3, x 520 . . 22 4.— E. Jenneri Arch, x 400 (after Ralfs) . 22 5-6. — E. aboense Elfv. 5, x 520; 6, vertical view, x 500 (after Elfving) . . .23 7-8.— E. inerme (Ralfs) Lund, x 430 . 24 9. — E. cuneatum Jemier. x 520 . . 25 10-13.— .E/. ansatum Ralfs. 10 and 12, x 430; 11, x 520; 13, zygospore, x 430 . 27 14-15. — E. ansatum var. pyxidatum Delp. 14, x 416 (after Delponte) ; 15, x 520 . .29 16-17. — E. obesum Josh. 16, x 300 (after Joshua) ; 17, x 520 . . .29 Plate 37 PLATE XXXVII. FIGS. PAGE 1. — Euastrum pingue Elfv. x 520 . . 30 2-5.— #. insigne Hass. 2, x 430 ; 3-5, x 520. Fig. 5 is a stouter form than fig. 2, but all inter- mediate forms exist . . .31 6. — E. intermedium Cleve. x 520 . .33 7. — E. Webbianum Turn, (forma major Turn.). x 400 (after Turner) . . .34 8. — E. Sendtnerianum Reinsch. x 1200 approx. (after Beinsch) . . .34 9-10.— E. TurneriiWest, 9, x 400; 10, x 430 . 37 11-13.— E. rostratum Ralfs. 11, x 400 (after Ralfs) ; 12 and 13, x 520 . . .35 14-15. — E. spinosum Ralfs. 14, x 400 (after Ralfs) ; 15 x 520 . . . 38 16-19.—^. Udentatum Nag. 16-18, x 430; 19, zygo- spore, x 520 . . . .39 Plate 38 PLATE XXXVIII. FIG. PAGE 1. — Euastrumpictum~BoYg. x 555 (after Borgesen) 41 2. — E. pictum forma, x 430 . . .42 3-4. — E. divaricatum Lund. 3, x 400 (after Lundell); 4, x 520 . . .. .42 5-8.— .E. dubium Nag. 5 and 6, x 520; 7 and 8, x 430 43 9. — E. dubium var. anglicanum (Turn.) West & Gr. S. West, x 500 (after Turner) . . 44 10. — E. dubium var. cambrense (Turn. )West & Gr. S. West, x 500 (after Turner) . . 45 11. — E. dubium var. Snowdoniense (Turn.) West & Gr. S. West, x 500 (after Turner) . 45 12-13. — E. erosum Lund. 12, x 400 (after Lundell) ; 13, x 400 . . .45 14_15._^. pukhellum Breb. 14, x 520; 15, x 430 . 46 16-21.— E. elegans (Breb.) Kiitz. 16 and 18, x 430 ; 17, 19, and 20, x 520; 21, x 625; 18 and 19, zygospores. Fig. 20 is an abnormal, much rounded form . 48 22-23. — E. elegans var. pseudelegans (Turn.) West & Gr. S. West. 22, x 500 (after Turner) ; 23, x 520 . . . .49 24-25. — E. elegans var. Novse Semlise Wille. x 520 . 49 26. — E. elegans var. ornatum West, x 520 . 50 27. — E. elegans var. ornithocepJialum (Benn.) West & Gr. S. West, x 400 (after Bennett) . 50 28-29.— E. binale (Turp.) Ehrenb. x 520 . .51 30. — E. binale forma sect a Turn, x 400 . . 53 31-32. — E. binale forma Gutwinskii Schmidle. x 520; 32, zygospore . . . .53 33. — E. binale forma hians West, x 400 . 53 34. — E. binale var. retusum West, x 520 . 54 35. — E. binale var. elobatum Lund, x 400 (after Lundell) . . . .54 36. — E. binale var. subelobatum West, x 400 . 55 37. — E. minutissimum West & Gr. S. West, x 500 (after Turner) . . . .57 Plate 39 PLATE XXXIX. PAGE 1-4. — Euastrum denticulatum (Kirchn.) Gay. 1-3, x 520 ; 4, x 430 . . .56 5. — E. denticulatum var. granulatum West, x 400 57 6-7. — E. incavatum Josh. & Nordst. 6,, x 400 ; 7 ', x 570 (after Nordstedt) . . 58 8-9.— E. montanum West & G. S. West, x 520 . 58 10-12.— E. pectinatum Breb. 10, x 430; 11 and 12, zygospores; 11, x 400; 12, x 520 . 60 13-15. — E. pectinatum var. inevolutum West & G. S. West. 13 and 14, x 430; 15, x 520 . 61 16. — E. pectinatum var. brachylobum Wittr. x 400 (after Wittrock) . . .62 17. — E.craftsangulatumHorg. x 555 (after B or ge sen) 70 18. — E. crassangulatum var. ornatum West. x 400 70 19. — E. gemmatum Breb. a and c, x 430 : b} vertical view of another specimen, x 520 . . 63 .—^/. occidentale West & G. S. West, x 430 67 a. Plate 40 PLATE XL. FIGS. PAGE 1. — Euastrum verrucosum Ehrenb. x 430 . 64 2-3. — E. verrucosum var. red/upturn Nordst. 2, x 520 ; 3, x 400 (after Nordstedt). In fig. 2 there is a great reduction of the polar lobe . 65 4. — E. verrucosum var. coarctatum Delp. x 400 . 66 5. — E. verrucosum var. coarctatum Delp. forma. x 400 . . . .66 6. — E. verrucosum var. (datum Wolle. x 430 . 67 7. — E. verrucosum var. planctonicam West & G. S. West, x 430 . . . . 67 8.—E. Cornubiense West & G. S. West, x 520 . 70 9-10. — E. crassicolle Lund. 9, x 400 (after Lundell) ; 10, x 520 . . . 71 11-13.— E. insulare (Wittr.) Roy. 11, x 400 (after Wittrock) ; 12 and 13, x 520 . 68 14. — E. insulare (Wittr.) Roy forma . . 69 15-18. — E. crispulum (Nordst.) West & G. S. West. All x 520 . . . 72 W.—E. stiblobatum Breb. x 520 . . 73 20. — E. sublobatum var. subdissimile West & G. S. West . . . .74 21-22.— -E/. validum West & G. S. West, x 520 75 Plate 41 PLATE XLI. FIGS. PAGE 1-4. — Micrasterias oscitans Ralfs. 1-3, x 200 (after Ralfs) ; 4, x 520 . . . 78 5-6. — M. oscitans var. mucronata (Dixon) Wille. 5, x 220; 6, x 430 . . .79 -11.— M. pinnatifida (Kiitz.) Ralfs. 7 and 8, x 430; 9 and 10, x 400; 11, vertical view, x 520 . 80 12. — M. pinnatifida forma. x 400 . . 82 13. — M. pinnatifida. Zygospore, x 520 . . 81 Plate 42 PLATE XLII. FIGS. PAGE l-8.~Micrasterias truncata (Corda) Breb. 1, 3-6, and 8, x 220; 2 and 7, x 400 . . 8JL/ 9. — M. truncata var. Bdhusiensis Wittr. x 200 (after Wittrock) . . .85 10-13.— M. crenata Breb. 10 and 11, x 200 (after Ralfs) ; 12 and 13, x 520 . . 85 U.—M. Jenneri Ralfs. x 520 , 86 .TI-; xi.u. 12. 14- Plate 43 PLATE XLIIL FIGS. PAGE 1-2. — Micrasterias Jenneri Ralfs. 1, x 400 ; 2, ver- tical view, x 300 . . .86 3. — M. Jenneri var. simplex West, x 400 . 88 4-8. — M. conferta Lund. 4-6, x 200 (after Lundell) ; 7 and 8, x 520. Fig. 4 has not been well executed, the lobulation being somewhat in- exact . . . .88 9. — M. conferta forma, x 520. This specimen is intermediate between the typical form and var. hamata . . . .90 10-11. — M. conferta var. hamata Wolle. 10, x 520; 11, larger specimen, x 430 . . 90 n,.- .in. 1 1 Plate 44 PLATE XLIV. PIGS. PAGE 1-2. — Micrasterias papillifera Breb. x 400 . .91 3. — M. papillifera forma major. x 220 . .92 4-5. — M. papillifera var. glabra Nordst. 4, x 520 ; 5, x 400 . . .93 6. — M. papillifera var. varvicensis Turn, x 250 (after Turner) . . . .93 7. — M. papillifera. Zygospore, x 200 (after Ralfs) 91 X1.1V. Plate 45 PLATE XLY. FIGS. PAGE 1-3. — Micrasterias Murrayi West & Gr. S. West. 1, x 300 ; 2 and 3, x 430 . . .93 4. — M. Murrayi var. triquetra West & G. S. West. x 520 . . . .94 5-6.— M. truncata (Corda) Breb. x 220 . . 82 7. — Euastrum sublobatum Breb. var. dissimile Nordst. x 570 (after Nordstedt). This figure (espe- cially fig. 7 a of the front view) has not been correctly executed . . .74 \TK V 6 . Plate 46 PLATE XL VI. FIGS. PAGE 1-2. — Micrasterias Sol (Ehrenb.) Kiitz. x 350 . 95 3-4. — M. Sol var. ornata Nordst. 3, x 275 (after Nordstedt) ; 4, small form, x 520 . . 97 5. — M. apiculata (Ehrenb.) Menegli. var. brachyptera (Lund.) West & G. S. West, x 200 . 97 6. — Polar lobe of a form of M. apiculata v&r.jimbriata (Ralfs) Nordst. x 400 . . " .99 ;,vi . d Plate 47 PLATE XLVIL FIGS. PAGE 1-2. — Micrasterias apiculata (Ehrenb.) Menegh. 1, x 250 (after a drawing by Turner) ; 2, x 170 . 97 (In fig. 1 we think the size of the teeth on the polar lobe has been somewhat exaggerated by Turner.) 3-4. — M. apiculata var. fimbriata (Ralfs) Nordst. 3, x 200 (after Ralfs) ; 4, x 200 (after Nordstedt) 99 5. — M. apiculata var. fimbriata forma spinosa Bissett. x 200 (after Bissett) . . .100 6. — M. apiculata var. brachyptera (Lund.) West & a. S. West, x 200 (after Lundell) . 101 7. — M. apiculata var. brachyptera (Lund.) West & G. S. West. A smooth form (forma gldbrius- cula Nordst.) x 200 (after Nordstedt) . 102 ri.ATK XLYJ.l ^ Plate 48 PLATE XLVIIL FIGS. PAGE 1-6. — Micrasterias rotata (Grrev.) Ralfs. 1, x 500 ; 2 and 3, polar lobes of two individuals, x 220 ; 4, vertical view, x 200 (after Archer) ; 5, side view, x 200 (after Archer) ; 6, zygo- spore, x 400 (after Lundell) . . 102 Mil. » oc Plate 49 PLATE XLIX. FIGS. PAGE 1-7. — Micrasterias denticulata Breb. 1, x 400 ; 2 and 3, polar lobes of two individuals, x 220 , 4, vertical view ; 5, side view ; 6, basal view of semicell; 4-6, x 200 (after Archer). 7, zygospore, x 400 (after Ealfs) . .105 PLATE \UX Plate 50 PLATE L. FIGS. PAGE 1-2. — Micrasterias denticulata Bret). 1, x 200; 2, zygospore, x 120 . . .105 3-4. — M. denticulata var. angulosa (Hantzscli) West & &. S. West. 3, x 200 ; 4, zygospore, x 200 (after Eoy & Bissett) . . .107 5. — M. denticulata var. angustosinuata Gay. Portion of semicell, x 400 . . .108 6. — M. denticulata var. notata ISTordst. Qa, x 300 ; 66, x 180 . . . 108 7. — M. denticulata var. subnotafa West. Vertical view, x 220 . . . . 108 1'L.YIT. L Plate 51 PLATE LI. FIGS. PAGE 1. — Micrasterias cornuta Benn. x 200 (after Bennett) 124 2. — M. verrucosa Bissett. x 200 (after Bissett) . 109 3-6. — If. Thomasiana Archer. 3 and 4, x 200 (after Archer) ; 5, x 400; 6, basal view of semi- cell with reduced processes, x 170 .110 7. — An intermediate form between M. Thomasiana and M. denticulata. x 170 112 I.I G. Plate 52 PLATE LII. FIGS. PAGE 1-9. — Micrasterias radiata Hass. 1, x 400 ; 2, x 520 ; 3, basal view of semicell, x 520 ; 4; x 200 ; 5; specimen showing reduction of divisions of lateral lobes, x 300; 6, x 200; 7, drawing of an American specimen which approaches M. dichotoma Wolle ; 8 and 9, abnormal con- ditions of lateral lobules, x 400 . .113 PLATE LIT '• Plate 53 PLATE LIIL FIGS. PAGE 1-2. — Micrasterias Cnix-Melltensis (Ehrenb.) Hass. 1, x 520; 2, x 400 . 116 3. — M. Crux-Melitensis. Form showing further divi- sion of lateral lobules, x 400 . .116 4-5. — M. Americana (Ehrenb.) Ralfs. 4, x 520 ; 5, x 400 . . . . . 117 6. — J/. Americana var. Boldtii Gutw. x 400 120 PLATE L1J1. Plate 54 PLATE LIV. FIGS. PAGE 1-3. — Micrasterias Americana (Ehrenb.) Ealfs. x 520. 2, vertical view ; 3, side view of semicell . 117 4. — M. Americana var. recta Wolle. x 400 . 119 5-6. — M. Americana var. Lewisiana West, x 400 . 120 7-8. — M. MahabulesJiwarensis Hobson var. Wallichii (G-run.) West & G. S. West. 7, x 200; 8, x 430 . . . 122 PLATE L1V Plate 55 PLATE LY. FIGS. PAGE 1-3. — Micrasterias Mahabuleshwarensis Hobson var. WaUichii (Grun.) West & G. S. West. 1, vertical view, x 520 ; 2 and 3, abnormal semi- cells from the plankton of Loch Bhaic, Scot- land, showing malformation of both lateral and polar lobes, x 520 . . 122 4. — Euastrum crassum (Breb.) Kiitz. var. Taturnii „ West & G. S. West, x 520 8 1'l.ATK L Plate 56 PLATE LVI. FIGS. PAGE 1-3. — Cosmarium obsoletum (Hantzscli) Reinsch. x 520 . . • 133 4. — C. obsoletum. x 520. A large tropical form from Ceylon showing the large pore in the thickening of the basal angles of the semicells. This form has been named "var. Sitvense" by Gutwinski . 134 5.__C. Smolandicum Lund, x 400 (after Lundell) . . 134 6-7. — C. Smolancticum var. angustatum West & G. S. West, x 400 . 135 8-10. — C. taxichondriforme Eichler & Gutw. 8, x 750 (after Eichler and Gutwinski) ; 9 and 10, x 400 . . 136 11, 13, 14.— C. circulare Reinsch. 11, x 960 (after Reinsch) ; 13 and 14, x 400 136 12. — C. circulare forma minor, x 1200 (after Raciborski) . . . .137 PLATE LVI Plate 57 PLATE LVIL FIGS. PAGE 1-2. — Cosmarium Lundellii Delp. x 412 (after Del- ponte) . . . .138 3-4. — C. Liindellii var. ellipticum \Vest. 3, x 400 ; 4, x 520 . . . 138 5—6. — C. Lundellii var. corruptum (Turn.) West & Gr. S. West, x 520. . . . 139 7. — C. pachydermum Lund, x 400 (after Lundell) . 8-9. — C. pachydermum var. aethiopicum West & Gr. S. 139 West, x 520 . " . . .140 10.— C. Ralfsii Breb. x 400 . .141 PLATE I A' II. Plate 58 PLATE LVIIL FIGS. PAGE l-2.—CosmariumRalfsiiHre>b. x 400 . . 141 3. — C. Ralfsii var. montanum Racib. x 400 . 142 4-5. — G. perforatum Lund. 4, x 520 ; 5, x 400 (after Lundell) . . . . 143 6. — C. ocellatum Eicliler & Glutw. 6d, x 750 ; 6a' and 6&, x 1000 (after Eicliler and Ghitwinski) 144 7. — C. ocellatum var. incrassatum West& G. S. West. x 520 . . . . 144 8-9. — C. cycliciim Lund. 8, x 400 (after Lundell) ; 9, x 400 . . . 145 10. — C. cyclicum var. arcticum Nordst. x 400 (after Nordstedt) . . . .146 11. — C. cyclicum var. arcticum Nordst. forma. x 400 (after Roy and Bissett) . . .146 12. — C. cyclicum var. Nordstedtianum (Reinsch) West & &. 8. West, x 520 146 M.ATK mil 2 . 11. 10 12. Plate 59 PLATE LIX. FIGS. PAGE 1-5. — Cosmarium undulatum Corda. All x 400. I, 4, and 5, after Ralfs . . .148 6-7. — C. undulatum var. minutum Wittr. 6, x 400 (after Wittrock) ; 7, x 1280 (after Kaciborski) 149 8-10. — C. undulatum var. Wollei West. 8 and 9, x 500 (after Wolle) ; 10, zygospore, x 400 (after Ralfs) .... 150 11-12. — C. undulatum var. crenulatum (Nag.) Wittr. II, x 500; 12, x 600 (after Nageli) . 150 13-15. — C. subundulatum Wille. 13, x 480 (after Wille); 14, x 600; 15, x 400 . . 151 IQ-tf.—C.fontigenum Nordst. 16, x 520; 17, x 500 (after Norstedt) . . .147 18-20.— C. Cucumis (Corda) Ealfs. 18, x 400 (after Gay) ; 19 and 20, x 400 (after Ralfs) . 152 21-22. — C. Cucumis var. magnum Racib. 21, x 520; 22, x 400 . . . 154 PLATE LIX 2.0. lei. 21. P.V7 Plate 60 PLATE LX. FIGS. PAGE 1-3. — Cosmarium Subcucumis Schmidle. 1, x 450 (after Schmidle) ; 2 and 3, x 520 . . 155 4. — C. Subcucumis ? x 520. This individual shows an intermediate condition between axile and parietal chloroplasts . .156 5—8. — C. microsphinctum ISTordst. 5 and 6, x 400 (after Nordstedt) ; 6, zygospore ; 7 and 8, x 520 . . . . 156 9. — C. microsphinctum foTm&parvulaWille. x 330 (after Wille) .... 157 10. — C. microspliinctum var. majus Roy & Biss. x 400 (after Roy) . . .157 11. — C. morsum West, x 520 . . . 157 12-14.— C. Pliaseolus Breb. 12, x 400 (after Ralfs) ; 13, x 400 ; 14, zygospore, x 500 (after Wolle) . ' . . .158 15. — C. Phaseolus forma minor Boldt. x 520 . 159 16-17. — C. Phaseolus var. elevatum Nordst. 16, x 570 (after Nordstedt) ; 17, x 520 . . 159 18. — C. tumidum Lund, x 400 (after Lundell) . 160 19. — C. tumidum forma subrectangularis West & G. S. West, x 400 . . 161 20.— C. Trafalgaricum Wittr. x 400 (after Witt- rock) .... 161 21-23. — C. melanosporum Arch. 21 and 22, x 600 (after Roy) ; 23, x 520 ; 22 and 23, zygo- spores . . . .162 24-25. — C. a&phserosporum Nordst. x 570 (after Nordstedt). 25, zygospore (z, front view; 2', end view; z' ', side view) . .163 26-27.— C. aspJiserosporum var. strigosum Nordst. 26, x 600 (after Nordstedt) ; 27, x 520 . 164 51. 20 a Plate 6 PLATE LXI. FIGS. PAGE 1-2. — Cosmarium inconspicuum West & G-. S. West. x 520. 2, zygospore . . .164 3-7.— C. Uoculatum Breb. 3-6, x 520; 7, x 400; 5-7, zygospores ; 7, after Kalfs . .165 8-9. — C. bioculatum forma depressa Schaarschm. 8, x 800 (after Schaarschmidt) ; 9, x 520 . 166 10-11. — C. bioculatum var. liians West & G. S. West. x 520 166 12-15.— C. tenue Arch. 12, 14 and 15, x 400; 13, x 600 . . . . 167 16-18.— C. tinctum Kalfs. 16, x 600; 17 and 18, zygo- spores, x 400 (after Ralfs) . .168 19-20. — C. tinctum var. intermedium Nordst. 19, x 520; 20, x 570 (after Nordstedt) . . 169 21-22.— C. flavum Roy & Biss. x . 400 (after Roy). 22, zygospore . . . .170 23-25.— C. contractual Kirclin. 23, x 500; 24 and 25, x 400 . . . 170 26. — C. contraction forma Jacobsenii (Roy) West & G. S. West, x 400 (after Jacobsen) . 171 27. — C. contractual var. Gartanewse West & G. S. West, x 520. . . .173 28. — C. contractual var. ellipsoideum (Elfv.) West & G. S. West, x 500 (after Elfving) . 172 29. — C. contraction var. ellipsoideum forma retusa West & G. S. West, x 520 . .173 30-32, — C. contractual V&Y. ellipsoideum forma (1). x 520 173 33. — C. contractual var. ellipsoideum forma (2). x 520 173 34. — Zygospore of C. contraction. x 400 . 171 35. — Zygospore of C. contractual var. ellipsoideum. x 400 (after Liitkemiiller) . .172 36-37.— C. subcontractum West & G. S. West, x 400. 174 38. — C. subaversum Borge. x 740 (after Borge) . 174 Fl- XI 18. -N li). r\& 10. 21. 11. 9. 26. 24-. 28. 33 . 38. 30. Plate 62 PLATE LXII. FIGS. PAGE 1. — Cosmarium tetraclwndrmn Lund, x 400 (after Lundell) . . . .175 2-5. — C. depressum (Nag.) Lund. 2, x 300 (after Xao-eli) ; 3 and 4, x 416 (after Delponte) ; 5, x 520 . . .176 6-9. — C. depressum var. achondrum (Boldt) West & G. 8. West. 6, x 400 (after Boldt); 7-9, x 520 . . . . 177 10. — C. depressum var. reniformt West & G. 8. West. x 520 . . . . 178 11—13. ~C. subquadrans West & Gr. 8. West. 11, x 500; 12 and 13, x 400 . . . 178 14-16. — C. succisum West. 14, x 400; 15 and 16, x 520 . . . . . 179 17-18.— C. retusiforme (Wille) Gutw. 17, x 480 (after Wille) ; 18, x 520 . . .180 19.— C. subretusifurme West & a. 8. West, x 830 . 180 20-21. — C. Hammeri Reinsch. 20, x about 550 (after Reinsch) ; 21, x 520 . . .181 22-23. — C. Hammeri var. homalodermum (Nordst.) West & Gr. 8. West. 22, x 400 (after Xordstedt) ; 23, x 330 (after Wille) . . . 182 24-25. — C. Hammeri var. protuberans West & Gr. 8. West, 24, x 520; 25, zygospore, x 400 . 183 26-27.— C. Nymannianum Grim. x 520 . . 184 28-30.— C. trilobulatum Reinsch. 28 and 29, x 520; 30, x about 1260 (after Reinsch) . . 185 s. .12 . •'' M ' 16. c ±3. 19. 20. 21 24. 22. 2G. >' 23. 27. 25. 2.8. Plate 63 PLATE LXIII. FIGS. PAGE 1-4. — -Costmarium granatum Breb. 1, x 400 (after Balfs) ; 2-4, x 520 . . 186 5-8. — C. granatum var. siibgranatum Nordst. 5, x 570 (after Nordstedt) ; 6-8, x 520 ; 8, zygo- spore .... 188 9. — C. granatum var. Grunowii Roy & Biss. x 400 (after Grunow) . . .189 10. — C. granatum var. elongatum Nordst. x 400 (after Nordstedt) . . .189 11-15. — C. Pokornyanwn (Grim.) West & G. S. West. 11, x 400 (after Wittrock) ; 12, x 400 (after Nordstedt); 13, x 400; 14 and 15, x 520 . 190 16-17. — C. pseudatlanthoideum West, x 520 . 191 18-20.— C. suUumidum Nordst. 18, x 400 (after Nordstedt) ; 19 and 20, x 520 . . 192 21—23. — C. subtumidum var. Klebsii (Ghitw.) West & G. S. West, 21, x 535 (outline, after Gut- winski) ; 22 and 23, x 520 . .193 24-25.— C. galeritum Nordst. 24, x 400 (after Nord- stedt) ; 25, x 400 . . .194 26. — C. pseudonitidulum Nordst. x 400 (after Nordstedt) .... 195 27-30. — C. pseudonitidulum var. validum West & G. S. West. 27-29, x 520; 30 x 400 (after Nordstedt) . . . .196 8. 16. 19. 24- Plate 64 PLATE LXLV. FIGS. PAGE 1—3. — Cosmarium nitidnliim De Not. 1, x 500 (after Wolle) ; 2, x 400 (after Nordstedt) ; 3, x 520 197 4.— C. cunaliculatum West & G. S. West. x 625 . 198 5-7. — C. pyramidatum Breb. 5, x 500; 6, x 400; 7, side view, x 400 (after Ralfs) . ' .199 8. — C. pyramidatum var. angustatum West & G. S. West, x 520. . . . 200 9-12. — C. pseudopyramidatum Lund. 9, x 400 (after Lundell) ; 10-12, x 520; 12, zygospore . 201 13. — C. pseudopyramidatum var. stenonotum Nordst. x 400 (after Nordstedt) . . .202 14-16. — C. variolatum Lund. 14, x 400 (after Lundell) ; 15, x 400; 16, x 520 . . . 203 17. — Euastrum pnlcliellum Breb. var. retusum West & G. S. West, x 400 46 8, JO. 32. 13. ir, . RAY SOCIETY INSTITUTED 1844 FOR THE PUBLICATION OF WORKS ON NATURAL HISTORY ANNUAL SUBSCRIPTION ONE GUINEA LIST OF THE SOCIETT FOR THE YEAR l<)n:> T WITH A LIST OF THE PUBLICATIONS CORRECTED TO OCTOBER, 1905 OFFICERS AND COUNCIL. 1905—1906. $ resident. THE RT. HON. LORD AVEBURY, D.C.L., LL.D., PRES.SOC.ANT., FOR.SEC.R.A., F.R.S., F.L.S., ETC. REV. CANON XORMAX, M.A., D.C.L., LL.D., F.R.S. ALBERT D. MICHAEL, F.L.S., F.Z.S. THE RT. HON. LORD WALSIXGHAM, M.A., LL.D., F.R.S. Council. ROBERT BRAITHWAITE, M.D., F.L.S. J. S. PHENE, LL.D., F.S.A. T. A. CHAPMAN, M.D., F.Z.S. Prof. EDWARD B. POULTON, M.A., Rev. ALFRED FULLER, M.A., F.E.S. Sc.D., LL.D., F.R.S. SIDNEY F. HARMER, Sc.D., F.R.S. HENRY POWER, M.B., F.L.S., F.Z.S. Prof. W. A. HERDMAN, D.Sc., F.R.S., P. H. PYE- SMITH, M.D., B.A., F.R.S.E., Pres.L.S. F.R.C.P., F.R.S. B. DAYDON JACKSON, F.L.S. D. H. SCOTT, M.A., Ph.D., F.R.S., ALBERT H. JONES, F.E.S. F.L.S., Pres.R.M.S. HENRY LAVER, M.R.C.S. HENRY SPICER, B.A., F.L.S., F.G.S. J. W. S. MEIKLEJOHN, M.D., F.L.S. ALFRED 0. WALKER, F.L.S., F.Z.S. (treasurer. F. DuCANE GODMAX, D.C.L., F.R.S., F.L.S., F.G.S. JOHN HOPKIXSOX, F.L.S., F.G.S., V.P.R.Met.Soc., Assoc. Inst.C.E.. Weetwood, "Watford. LIST OF THE BAY SOCIETY. Aberdeen, University of; King's College, Aberdeen. Adelaide Public Library; Adelaide, S. Australia. Adkin, Robert, F.E.S. ; Welljield, 4 Lingards Road, Lewisham, Adlard, R, E. ; Bartholomew Close, E.G. Advocates' Library ; Edinburgh. Albany Museum ; Grahamstown, Cape Colony, S. Africa. Andrews, Arthur; Newtoicn House, Blachrock, Dublin. Armstrong College ; Newcastle-upon-Tyne. Army and Navy Club ; 36 Pall Hall, S.W. Ash, The Rev. Cyril D. ; Ship with Vicarage, SeJby. Athenaeum Club ; Pall Hall, S.W. Australian Museum; Sydney, New South Wales. Avebury, The Right Hon. Lord, D.C.L., LL.D., F.R.S., F.S.A., F L.S., F.G.S., F.Z.S., F.E.S., PRESIDENT ; 15 Lombard Street, E.G. ; 6 St. James's Square, S.W. ; and High Elms, Farnborough, R.S.O., Kent. Baer, Joseph, & Co. ; 6 Hochstrasse, Frankfort, Germany. Barrow-in-Furness Public Library ; Barrow-in-Furness. Battersea Public Library; Lavender Hill, S.W. Belfast Library; Donegal Square, Belfast. Bentley, Richard, F.S.A., F.L.S., Pres.R.Met.Soc., F.R.G.S.; The Here, Upton, Slough. Berens, A. A., M.A. ; Castlemead, Windsor. Bergen Museum ; Bergen, Norway. Berlin Royal Library ; Berlin. Berlin Royal Zoological Museum ; Berlin. Berne Natural History Museum ; Berne, Switzerland. Bethune-Baker, George T., F.L.S., F.E.S.; 19 Clarendon Road, Edgbaston, Birmingham. 6 LIST OF THE EAY SOCIETY. Bibliotheque Rationale ; Paris. Binks, Mrs. I.; 9 Burton Street, Wakefield. Birmingham Free Libraries; Birmingham. Birmingham Library ; Margaret Street, Birmingham. Blackburne-Maze, W. P., F.E.S.; Shaw House, Newbury. Bloomfield, The Rev. E. N., M.A., F.E.S. ; Guestling Rectory, Hastings. Board of Education, Secondary Branch; South Kensington, s.w. Bodleian Library ; Oxford. Bootle Free Library ; Oriel Road, Bootle, Liverpool. Borgesen, Dr. F. ; Botanic Library, Copenhagen. Bostock, E. ~D., F.E.S. ; Holly House, Stone. Boston Public Library; Boston, Mass., U.S.A. Bourne, T. W. ; The Wold, Kin gs~ker swell, Newton Abbot. Bradford Natural History and Microscopical Society ; Church Institute, North Parade, Bradford. Brady, Gr. Stewardson, M.D., LL.D., F.E.S., Professor of Natural History, Durham College of Science ; 2 Mowbray Villas, Sunderland. Braithwaite, Robert, M.D., M.R.C.S.E., F.L.S.; 26 Endymion Road, Brixton Hill, S.W. Breslau University Library ; Breslau, Germany. Briggs, C. A., F.E.S. ; Rod: House, Lynmouth, R.S.O., North Devon. Briggs, T. H., M.A., F.E.S.; Rock House, Lynmouth, R.S.O., North Devon. Brighton and Hove Natural History Society; Public Library , Brighton. Bristol Museum and Reference Library; Queen's Road, Bristol. British Museum; Bloomsbury, W.C. Brockholes, Mrs. J. Fitzherbert; Clifton Hill, Garstang, R.S.O., Lancashire. Bromley Naturalists' Society; 92 London Road, Bromley, Kent. Brussels National Library ; Brussels. Buchan-Hepburii, Sir Archibald, Bart., F.E.S. ; Smeaton- Hepburn, Preston'kir'k, N.B. Burrows, The Rev. C. R. N. ; Mucking Vicarage, Stanford-Ie- Hope, s.o., Essc,<\ LIST OF THE HAY SOCIETY. 7 Cambridge Pliilosopliical Library ; New Museums, Cambridge. Cambridge University Library ; Cambridge. Campbell, F. Maule, F.L.S., F.Z.S., F.E.S., F.E.M.S. ; Brynllwydwyn, Machynlleth. Canterbury, Philosophical Institution of; Christchurch, New Zealand. Cardiff Free Libraries ; Cardiff. Carlyon, T. A.; Connemara, Darracott Road, Boscombe Park, Bournemouth. Chapman, Edward, M.A., F.L.S. ; Hill End, Mottram, Man- chester. Chapman, T. Algernon, M.D., F.Z.S., F.E.S. ; Betula, Reigate. Chawner, Miss Ethel F., F.E.S. ; Forest Bank, Lyndhurst, R.S.O., Hants. Cheltenham Natural Science Society ; Cheltenham. Chester Society of Natural Science ; Grosvenor Museum, Chester. Chicago Public Library ; Chicago, III., U.S.A. Christiania, University of ; Christiania, Norway. Church, Sir W. S., Bart., M.D. ; 130 Harley Street, W. Clark, J. A., L.D.S., F.E.S.; 57 Weston Park, Crouch End, N. Cleland, John, M.D., D.Sc., LL.D., F.R.S., Professor of Anatomy, University of Glasgow ; 2 The University, Glasgow. Congress, Library of; Washington, D.C., U.S.A. Cornell University Library ; Ithaca, New York, U.S.A. Cornwall, Eoyal Institution of ; Truro. Cotton, John, M.R.C.S., F.E.S. ; Simonswood, Prescot Road, St. Helens. Crawford, W. C. ; 1 Lockerton Gardens, Colinton Road, Edinburgh. Croft, E. Benyon, R.N. ; Fanhams Hall, Ware. Croydon Public Libraries; Town Hall, Croydon. Dames, Felix L. ; 12 Landgrafenstrasse, Berlin, W. 62. Davies, A. Ellson, Ph.D., F.L.S., F.C.S.; Tweedlank, West Savile Road, Edinburgh. Derby Free Library and Museum ; Wardwick, Derby. 8 LIST OF THE RAY SOCIETY. Detroit Public Library; Detroit, J//C/L, U.S.A. Devonshire, His Grace the Duke of, K.G., M.A., LL.D., F.R.S., Hon.M.Inst.C.E. ; Devonshire House, Piccadilly, W., and Chatsicorth, Derbyshire. Dickinson, William; Warham Road, Croydon. Downing College; Cambridge. Dublin, Royal, Society; Leinster House, Dublin. East Kent Natural History Society ; Medical Hall, Canter- bury. Eastwood, John E., F.E.S. ; Enton Lodge, Witley, Godalming. Edinburgh Public Library ; Edinbitrgh. Edinburgh, Royal Society of; Edinburgh. Edinburgh, University of ; Edinburgh. Elphinstone, Sir Howard W., Bart,', M.A., F.L.S., F.R.G.S. ; 2 Stone Buildings, Lincoln's Inn, W.C., and Struan, Wimbledon Park, S.W. England, Royal College of Surgeons of; Lincoln' s Inn Fields, w.c. Fielding, Clement, M.P.S. ; Clover Hill, Halifax. FitzGerald, The Rev. H. Purefoy, F.L.S., F.C.S. ; Barracane, Wellington College, s.o., Berks. Fletcher, W. H. B., M.A., F.E.S. ; Aldicick Manor, Bognor. Folkestone Free Public Library and Museum ; Folkestone. «/ Foster, C. ; Thorpe, Norwich. France, Institut de ; Paris. Fraser, F. J. ; 19 Southampton Street, Bloomsbury, W.C. Freeman, Francis F., F.E.S.; Abbotsjield, Tamstock. Friedlander & Sohn; 11 Carlstrasse, Berlin, N.W. 6. Fulham Public Libraries (Central Library) ; 598 Fulham Eoad, S.Wr. Fuller, The Rev. Alfred, M.A., F.E.S.; The Lodge, SydenJiam Hill, S.E. Gannett, Frank W. ; Dalegarth, Windermere. Gascoigne, Major French; Lotherton Hall, Aberford, Leeds. Geological Society of London ; Burlington House, Piccadilly } W. Gerold & Co. ; Vienna. LIST OF THE KAY SOCIETY. 9 Gibbs, Arthur Ernest, F.L.S., F.R.H.S., Hon. Sec. Herts Nat. Hist. Soc. ; Kitchener's Meads, St. Albans. Gibson., Miss ; Hill House, Saffron Walden. Giles, Harry M. ; Zoological Gardens, South Perth, Western Australia. Glasgow Natural History Society; 207 Bath Street, Glasgow. Glasgow, Royal Philosophical Society of; 137 West George Street, Glasgow. Glasgow, University of ; Glasgow. Godrnan, F. DuCane, D.C.L., F.R.S., F.L.S., F.G.S., F.Z.S., F.E.S., F.R.H.S., TEEASDEER; 7 Carlos Place, Grosvenor Square, W., and South Lodge, H or sham. Grottingen University Library ; Gottingen, Germany. Great Britain, Pharmaceutical Society of; 17 Bloomsbury Square, W.C. Green, E. Ernest, F.E.S., Government Entomologist ; Royal Botanic. Gardens, Peradeniya, Ceylon. Grosvenor Public Library; Buffalo, N.Y., U.S.A. Guille-Alles Library ; Guernsey. Haileybury College ; Hertford. Halifax Public Library ; Belle View, Halifax. Hardy, Alfred Douglas, F.L.S., F.R.M.S.; Lands Department, Melbourne, Victoria, Australia. Harley, John, M.D., F.R.C.P., F.L.S. ; Seeding*, Pulborough, R.S.O., Sussex. Harmer, Sidney F., Sc.D., F.R.S.; King's College, Cambridge. Harrison, Albert, F.L.S., F.E.S., F.RJM.S., F.C.S. ; Dela- mere, Grove Road, South Woodford. Harvard University Museum of Comparative Zoology ; Harvard, Cambridge, U.S.A. Hastings and St. Leonards Natural History Society; The Museum, Hastings. Heidelberg University ; Heidelberg, Germany. Hertfordshire County Museum ; St. Albans. Hertfordshire Natural History Society and Field Club ; Upton House, Watford. Hilton, James; 60 Montague Square, W. Hood, Donald W. C., M.D. ; 43 Green Street, Park Lane, W. 10 LIST OF THE EAY SOCIETY. Hooker, Sir Joseph Dalton, G.C.S.L, C.B., M.D., D.C.L., LL.D., F.E.S., F.L.S., F.G.S., F.R.G.S.; The Camp, Sunningdale, Ascot. Hope, G. P. ; Havering Grange, Romford. Hopkinson, John, F.L.S., F.G.S., F.E.M.S., Y.P.R.Met.Soc., Assoc.Inst.C.E., SECRETARY; Weetwood, Watford, and 84 New Bond Street, W. Huddersfield Naturalist and Photographic Society ; The Technical College, Huddersfield. Hull Public Libraries ; Hull. Ireland,, National Library of ; Kildare Street, Dublin. Irish, Royal, Academy; 19 Dan-son Street, Dublin. Jackson, B. Day don, F.L.S., General Secretary of the Linnean Society; 21, Cautlei/ Avenue, Clapham Common, S.W. John Crerer Library ; Chicago, III., U.S.A. Jones, Albert H., F.E.S. ; Shrublands, Eltham. Junk, W. ; 22 Ttathenowerstrasse, Berlin, N.W. 5. Justen, Frederick, F.L.S. ; 37 Soho Square, W. Ivenrick, G. H., F.E.S. ; Whetstone, Somerset Road, Edgbaston, Binning Ji a in. Kiel University Library ; Kiel, Germany. Kilmarnock Public Library and Museum; Kilmarnock, N.B. King's Inn Library ; Dublin. Knight, H. H. ; Bank House, Llandovery. Layer, Henry, M.E.C.S. ; 43 Head Street, Colchester. Lebour, Miss Marie Y., B.Sc. ; Baddiffe House, Corbridge, R.S.O., Northumberland. Leeds Philosophical and Literary Society; The Museum, Leeds. Leeds Public Free Libraries ; Leeds. Leeds, University of ; Leeds. Leicester Free Public Library ; Wellington Street, Leicester. Lemanii, F. C., F.E.S. ; Black Friars House, Plymouth. Lethbridge, Ambrose Y., F.E.S. ; Buckhurst, WoMngham, and Rokeby, Barnard Castle. Linnean Society of London; Burlington House, Piccadilly, W. LIST OF THE EAY SOCIETY. 11 Lister, Arthur, F.R.S., F.L.S. ; Sycamore House, Leytonstone, N.E., and High Cliff) Lyme Regis. Liverpool Athenaeum ; Liverpool. Liverpool Free Public Libraries ; Liverpool. Liverpool Microscopical Society; 20 Hackings Hey, Liverpool. London Institution ; Fiiixburij Circus, E.G. London Library; 12 St. James's Square, S.W. Long-staff, Gr. B., M.D. ; Highlands, Putney Heath, S.W. Los Angeles Public Library; California, U.S.A. Lyon Universite Bibliotheque ; Lyons, France. Mclntosh, W. Carmicliael, M.D., LL.D., F.R.S.L.&E., F.L.S., Professor of Natural History, University of St. Andrews; 2 Abbotsford Crescent, St. Andrews, N.B. McMillan, William Singer, F.L.S. ; Ardenholm, Maghull, Liverpool. Macvicar, Symers Macclonald, M.A. ; Invermoidart, Acharacle, E.S.O., Argyllshire. Magdalen College ; Oxford. Manchester Literary and Philosophical Society ; 36 George Street, Manchester. Manchester Public Free Libraries ; Manchester. Maryborough College Natural History Society; Marlborough. Massey, W. H. ; Twyford, E.S.O., Berks. Meiklejohn, J. W. S., M.D., F.L.S. ; 105 Holland Road, Kensington, W. Melbourne Public Library ; Melbourne, Australia. MennelJ, H. T., F.L.S. ; 10 St. Dunstan's Buildings, Great Tower Street, E.G. Michael, Albert D., F.L.S., F.Z.S., F.E.M.S., F.R.H.S., VICE- PRESIDENT; 9 Cadogan Mansions, Sloane Square, S.W., and The Warren, Studland, Wareham. Middlesborough Free Libraries; Middles-borough. Mitchell Library; 21 Miller Street, Glasgow. Morgan, Ralph ; 9 Clifton Hill, Exeter. Munich Royal Library ; Munich, Germany. Murray, James ; Challenger Office, Villa Medusa, Bosicell Road, Edinburgh; and Ardoch Nerston, East Kilbride, N.B. Museum d'Histoire Naturelle ; Paris. 1Z LIST OF THE BAY SOCIETY. Newcastle-upon-Tyne Literary and Philosophical Society ; Westgate Road, Newcastle-upon-Tyne. Newcastle-upon-Tyne Natural History Society ; Museum, Barras Bridge, Newcastle-upon-Tyne. Newcastle-upon-Tyne Public Library; Newcastle-upon-Tyne. New South Wales, Royal Society of; Sydney, N.8.W. Newstead, Robert, A.L.S., F.E.S., Hon.F.R.H.S. ; School of Tropical Medicine, The University, Liverpool. New York Botanical Garden ; Bronx Park, New York City, N.Y., U.&.A. New York Public Library; New York, U.S.A. New York State Library; Albany, N.Y., U.S.A. Noble, Sir Andrew, K.C.B., F.R.S.; Jesmond Dene House, Newcastle-on-Tyne. Norfolk and Norwich Library ; Norwich. Norman, The Rev. A. Merle, M.A., D.C.L., LL.D., F.R.S., F.L.S., Hon. Canon of Durham, VICE-PRESIDENT ; The Red House, Berlchamsted. Norwich Free Library ; Norwich. Nottingham Free Public Libraries; Nottingham. Okamura, Prof. K. ; 4 Ichibei-machi I, Azabu, Tokyo, Japan. Ontario Agricultural College ; Guelph, Canada. Otago, University of ; Dunedin, New Zealand. Owens College (Christie Library) ; Manchester. O \ i/ / ' Paisley Philosophical Institution; 3 County Place, Paisley. Peabody Institute; Baltimore, Maryland, U.S.A. Perthshire Society of Natural Science; Tay Street, Perth. Phene, J. S., LL.D., F.S.A. ; 5 Carlton Terrace, Oakley Street, S.W. Philadelphia Academy of Natural Sciences; Philadelphia, Pa., U.S.A. Pickard-Cambridge, The Rev. 0., M.A., F.R.S.; Bloxworth Rectory, Wareham. Plowman, T. ; Nystuen Lodge, Bycullah Park, Enjield. Plymouth Institution; Athenaeum, Plymouth. Portsmouth Free Public Library ; Town Hall, Portsmouth. Poulton, Edward B., M.A., Sc.D., LL.D., F.R.S., F.L.S., F.G-.S., F.E.S., Hope Professor of Zoology, University of Oxford; Wy'keliam House, Oxford. LIST OF THE EAY SOCIETY. 13 Power, Henry, M.B., F.R.C.S., F.L.S , F.Z.S. ; Bagdale Hall, Whitby. Preston Free Public Libraries and Museum ; Preston . Pye-Smith, P. H., M.D., B.A., F.R.C P, F.R.S.; 48 Brook Street, Cavendish Square } A\ . Quaritch, Bernard; 15, Piccadilly, A\ . Queen's College ; Belfast. Queen's College ; Cork. Quekett Microscopical Club ; 20 Hanover Square, TV. Radcliffe Library; Museum, Oxford. Rashleigli, Evelyn William; Stoketon, Saltash, Comical! . Reader, Thomas; Beaufort House, 125 Peckham Rye, S.E. Ripon, The Most Hon. the Marquis of, K.G-., K.C.S.I., D.C.L., F.R.S., F.L.S., F.G.S., F.Z.S. ; 9 Chelsea Embankment, S.~W.} and Studley Royal, Ripon. Rotherliam Naturalists' Society; Rotherham. e, Royal Academy of Sciences ; Amsterdam. Royal Academy of Sciences; Stockholm, Sweden. V «/ Royal College of Science; Dublin. Royal Institution of Great Britain ; Albemarle Street, W. Royal Microscopical Society; 20 Hanover Square, W. Royal Society; Burlington House, Piccadilly, W. St. Albans Public Library; St. Albans. St. Andrews University ; St. Andrews. N.B. */ * St. Catharine's College ; Cambridge. Salford Free Museum and Libraries ; Peel Park, Salford, Manchester. Salisbury Microscopical Society; Salisbury. Sanders, Alfred, M.R.C.S., F.L.S. ; The Han-thorns, Caterham Valley, s.o., Surrey. Scharff, R. F., Ph.D., B.Sc., F.L.S., F.Z.S.; Tudor House, Dundrum, E.S.O., co. Dublin. Sears, R. S. "\Vilson; 1 Lisbon Grove, Marylebone, N.AY. Sheffield Literary and Philosophical Society; Leopold Street. Sheffield. Schmidle, Prof. W., Seminar-Director; Meersburg-on-Eodensee, Baden, Germany. 1.4 LIST OP THE RAY SOCIETY. Schmidt, Max, Ph.D. ; Weg beim Tdger, Gross Borstel, bei Hamburg. Scottish, Royal, Museum ; Edinburgh. Sidney-Sussex College ; Cambridge. Sioii College Library ; Victoria Embankment, E.G. Soar, C. D. ; 37 DryburgJi Road, Putney, S.W. Somersetshire Archaeological and Natural History Society ; The Castle, Taunton. Southport Free Library ; Southport. Spicer, Henry, B.A., F.L.S., F.G-.S.; 14 Aberdeen Park, Highbury, N. Sprague, T. B., M.A., LL.D. ; 29 Buckingham Terrace, Edinburgh. Stazione Zoologica ; Naples. Stechert, G-. E. ; 2 Star Yard, Carey Street, W.C. Stoke Newington Public Libraries ; Church Street, N. Stubbins, J. ; Woodlands, Pool, Leeds. Simderland Library and Literary Society ; Fawcett Street, SuJiderlaud. Terry, C. ; Foxliill Grove, Bath. Toronto, University of ; Toronto, Canada. Torquay Natural History Society ; Museum, fiabbacombe Road, Torquay. Town, Miss ; 7 Oakroyd Villas, Bradford. Townshend, Frederick, M.A., F.L.S. ; Honington Hall, Shipston-on-Stour. Trinity College ; Cambridge. Trinity College ; Dublin. Trondhjem, Royal Library of; Trondhjem, Norway. Tunstall, Wilmot, F.E.S. ; Caerleon, G-reenlaw Drive, Paisley, KB. University College, London; G-oiver Street, W.C. Upsala, University of; Upsala, Sweden. Victoria Institute ; Worcester. Walker, Alfred 0., F.L.S., F.Z.S. ; Ulcombe Place, Maidstone. Walsingham, The Right Hon. Lord, M.A., LL.D., F.R.S., F.L.S., F.Z.S., F.E.S., A^ICE-PRESIDENT ; Merton Hall, Thetford, LIST OF THE KAY SOCIETY. 15 Warrington Municipal Museum; Warrington. Weg, Max ; 1, Leplaystrass, Leipzig. Wesley, E. R, A.K.C.; 28 Essex Street, Strand, W.C. West Kent Xatural History Society; Blaclcheath, S.E. Whittle, F. G-. ; 3 Marine Avenue, South end-on- Sea. "Wickes, W. D., F.L.S. ; 20 Warrior Square, South end-on- Sea. Wood, J. H., M.B.; Tarring ton, Ledbury. Woodd-Smittij Miss B. M.; 17 Langland Gardens, Hampstead, N.W. Yale University; New Haven, U.S.A. Yorkshire Philosophical Society; Museum, York. Zoological Society of London ; 3 Hanover Square, W. The Advocates' Library,, Edinburgh ; the Bodleian Library, Oxford ; the British Museum; Cambridge University Library; and Trinity College, Dublin, entered in the List, receive the Society's publications in accordance with the Copyright Act. LIST OF THE PUBLICATIONS OF THE BAY SOCIETY For the First Year, 1844. 1 Reports on the Progress of Zoology and Botany, 1841, 1842. viii + 496 + xx pp. 8vo. ° 1845. The State of Zoology in Europe, as regards the Vertebrata. By C. L. BONAPARTE. Transl. by H. E. STRICKLAND, pp. 1-44. The Progress of Zoology in 1842. Transl. from the German by W. B. MACDONALD. pp. 1-348. The Progress of Physiological Botany in 1841. By H. F. LINK. Transl. by EDWIN LANKESTER. pp. 1-104. Index, pp. i-xx. 2 A Monograph of the British Nudibranchiate Mollusca. By JOSHUA ALDER and ALBANY HANCOCK. Part I. x + 20 pp., 10 plates. Folio. 1845. 3 Memorials of JOHN RAY, consisting of his Life by Dr. DERHAM ; . . . with his Itineraries, etc. Edited by EDWIN LANKESTER. xii + 220 pp. 8vo. 1846. For the Second Year, 1845. 4 On the Alternation of Generations. By J. J. S. STEENSTEUP. Transl. from the German version of C. H. LORENZEN by GEORGE BUSK, viii + 132 pp., 3 plates. 8vo. 1845. 5 A Monograph of the British Nudibranchiate Mollusca. By JOSHUA ALDER and ALBANY HANCOCK. Part II. iv -f 34 pp., 13 plates. Folio. 184G. G Reports and Papers on Botany, viii + 494 pp., 7 plates. «Svo. 1846. On the Morphology of the Coiiiferse. By J. J. ZUCCAEINI. Transl. by GEORGE BUSK. pp. 1-54, 441-444, pis. i-v. Report on Botanical Geography, 1842. By A. GRISEBACH. Transl. by W. B. MACDONALD. pp. 55-212. Memoir on the Nuclei, Formation, and Growth of Vegetable Cells. By CARL NAGELI. Transl. by ARTHUR HENFREY. pp. 213-292, 445-459, pis. vi. vii. Report on Physiological Botany, 1842 and 1843. By H. F. LINK. Transl. by J. HUDSON, pp., 293-440. Index pp. 401-494. 18 PUBLICATIONS OF THE RAY SOCIETY. For the third Year, 1846. 7 Outlines of the Geography of Plants. By F. J. F. MEYEN. Transl. by MARGARET JOHNSTON, x -f 422 pp., 1 plate. 8vo. 1846. 8 The Organization of Trilobites. By HERMANN BURMEISTER. Edited by THOMAS BELL and EDWARD FORBES, xii + 136 pp., 6 plates. Folio. 1846. 9 A Monograph of the British Nndibranchiate Mollnsca. By JOSHUA ALDER and ALBANY HANCOCK. Part III. iv + 30 pp., 12 plates. Folio. 1847. For the Fourth Year, 1847. 10 Elements of Physiophilosophy. By LORENZ OKEN. From the German by ALFRED TULK. xx + 666 pp. 8vo. 1847. 11 Reports on Zoology for 1843, 1844. Transl. from the German by GEORGE BUSK, ALFRED TULK, and A. H. HALIDAY. viii + 596 pp. 8vo. 1847. Progress of Zoology in 1843. pp. 1-232. 1844. pp. 233-564. Index, pp. 565-596. 12 A Monograph of the British Naked-eyed Medusae. By EDWARD FORBES, viii + 104 pp., 13 plates. Folio. 1848. For the Fifth Year, 1848. 13 Bibliographia Zoologies et Geologise. A General Cata- logue of all Books, Tracts, and Memoirs on Zoology and Geology. By Louis AGASSIZ. Edited by H. E. STRICKLAND. Yol. I. Periodicals, and A-B. xxvi + 506 pp. 8vo. 1848. 14 The Correspondence of JOHN RAY. Edited by EDWIN LANKESTER. xvi -f 502 pp., 2 plates. 8vo. 1848. 15 A Monograph of the British Nndibranchiate Mollnsca. By JOSHUA ALDER and ALBANY HANCOCK. Part IV. iv -f 28 pp., 12 plates. Folio. 1848. For the Sixth Year, 1849. 16 Reports and Papers on Botany. Edited by ARTHUR HENFREY. viii + 514 pp., 3 plates. 8vo. 1849. On the Structure of the Palm-stem. By H. VON MOHL. pp. 1-92, 495, pi. i. On the Nuclei, Formation, and Growth of Vegetable Cells. By CARL NAGELI. Part II. pp. 93-158, 495-502, pis. ii, iii. On the Utricular Structures in the Contents of Cells. By CARL NAGELI. pp. 159-190. Report on Physiological Botany for 1844 and 1845. By H. T. LINK. pp. 191-314. PUBLICATIONS OK Till-] KAY SOCIETY. 19 Report on Geographical Botany for 1844. By A. GKISEBACH. pp. 315-414. Report on Geographical and Systematic Botany for 1845. By A. GKISEBACH. pp. 415-494. 17 The Natural History of the British Entomostraca. By \Y . I.>AU;D. viii 4- 364 pp., 36 plates. Svo. 1850. For the Seventh Year, 1850. 18 Bibliographia Zoologise et Greologise. A General Cata- logue of all Books, Tracts, and Memoirs on Zoology and Geology. By Louis AGASSIZ. Edited by H. E. STRICKLAND. Vol. U. C-F. iv + 492 pp. Svo. 1850. 19 A Monograph of the British Nudibranchiate Mollusca. By JOSHUA ALDER and ALBANY HANCOCK. Part V. iv + •/ 62 pp., 16 plates. Folio. 1851. For the Eighth Year, 1851. 20 The British Species of Angiocarpous Lichens, elucidated by their Sporidia. By the Eev. W. A. LEIGHTON. vi + 102 pp., 30 plates. 8vo. 1851. 21 A Monograph of the Sub-class Cirripedia. By CHARLES DARWIN. The Lepadidas, or Pedunculated Cirripedes. xii + 400 pp., 10 plates. 8vo. 1851. For the Ninth Year, 1852, H 22 Bibliographia Zoologia? et Geologise. A General Cata- logue of all Books, Tracts, and Memoirs on Zoology and Geology. By Louis AGASSIZ. Edited by H. E. STRICKLAND. Vol. III. G-M. vi + 658 pp. Svo. ' 1852. 23 A Monograph of the British Nudibranchiate Mollusca. By JOSHUA ALDER and ALBANY HANCOCK. Part VI. iv 4 62 pp., 12 plates. Folio. 1852. For the Tenth Year, 1853. 24 Botanical and Physiological Memoirs. Edited by ARTHUR HENFRKY. xvi + 568 pp., 6 plates. Svo. 1853. The Phenomenon of Rejuvenescence in Nature. By ALEXANDER BRATJN. pp. vii-xxvi, 1-342, pis. i-v. The Animal Nature of Diatomese. By G. MENIGHINI. pp. 343-514. The Natural History of Protococcus pluvialis. By FERDINAND COHN. pp. 515-564, pi. vi. 25 A Monograph of the Sub-class Cirripedia. By CHARLES DARWIN. The Balanidae, the Verrucidte, etc. viii + 684 pp. Svo. 1854. 20 PUBLICATIONS OF THE RAY SOCIETY. For the Eleventh Year, 1854. 26 Bibliographia Zoologias et Geologise. A General Cata- logue of all Books,, Tracts, and Memoirs on Zoology and Geology. By Louis AGASSIZ. Edited by H. E. STRICKLAND. Vol. IV. N-Z. vi + 604 pp. 8vo. 1854. For the Twelfth Year, 1855. 27 A Monograph of the British Nudibranchiate Mollusca. By JOSHUA ALDER and ALBANY HANCOCK. Part VII. vi -f 54 -f 40 + xlvi pp., 9 plates. Folio. 1855. For the Thirteenth Year, 1856. 28 A Monograph of the Fresh- water Polyzoa, including all the known species, both British and Foreign. By GEORGE JAMES ALLMAN. viii + 122 -f 22 pp., 11 plates. Folio. 1856 [1857]. For the Fourteenth Year, 1857. 29 The Recent Foraminifera of Great Britain. By WILLIAM CRAWFORD WILLIAMSON, xx -f 108 pp., 7 plates. Folio. 1858. For the Fifteenth Year, 1858. 30 The Oceanic Hydrozoa ; a Description of the Calyco- phoridse and Physophoridae. . . . By THOMAS HENRY HUXLEY, x + 144 + 24 pp., 12 plates. Folio. 1859. For the Sixteenth Year, 1859. 31 A History of the Spiders of Great Britain and Ireland. By JOHN BLACKWALL. [Part I.] vi + 174 -f 24 pp., 12 Plates. Folio. 1861. For the Seventeenth Year, 1860. 32 Introduction to the Study of the Foraminifera. By WILLIAM B. CARPENTER, assisted by WILLIAM K. PARKER and T. RUPERT JONES, xxii -f 320 4- 44 pp., 22 plates. Folio. 1862. For the Eighteenth Year, 1861. 33 On the Germination, Development, and Fructification of the Higher Cryptogamia, and 011 the Fructification of the Conifera). By WILHELM HOFMEISTER. Tran si. by FREDERICK CURREY. xviii + 506 pp., 65 plates. 8vo. 1862. PUBLICATIONS 01'' TIIM RAY SOCIETY. 21 For the Nineteenth Year, 1862. 34 A History of the Spiders of Great Britain and Ireland. By JOHN BLACKWALL. Part II. iv + 210 (175-384) + 34 pp., 17 plates. Folio. 1864. For the Twentieth Year, 1863. 35 The Reptiles of British India. By ALBERT C. L. G. GDNTHEK. xxviii -f 452 pp., 26 plates. Folio. 1864. For the T unity -first Year, 1864. 36 A Monograph of the British Spongiadae. By J. S. BOWERBANK. Vol. I. xx + 290 pp., 37 plates. 8vo. 1864. For the Twenty-second Year, 1865. 37 The British Hemiptera. Vol. I. Heiniptera-Heteroptera. By JOHN WILLIAM DOUGLAS and JOHN SCOTT, xii + 628 + 42 pp., 21 plates. 8vo. 1865. 38 A Monograph of the British Spongiadae. By J. S. BOWERBANK. Vol. II. xx + 388 pp. 8vo. 1866. For the Twenty -third Year, 1866. 39 The Miscellaneous Botanical Works of ROBERT BROWN. [Edited by JOHN J. BENNETT.] Vol. I, containing I, Geo- graphico-botanical, and II, Structural and Physiological Memoirs, viii + 612 pp. 8vo. 1866. 40 Recent Memoirs on the Cetacea. Edited by WILLIAM HENRY FLOWER, xii + 312 pp., 6 plates. Folio. 1866. I. On the Greenland Right- Whale. By D. F. ESCHRICHT and J. REINHARDT. pp. 1-150, pis. i-vi. II. On the Species of the Genus Orca inhabiting- the Northern Seas. By D. F. ESCHRICHT. pp. 151-188. III. Pseudorca crassidens, a Cetacean hitherto unknown in the Danish Fauna. By J. REINHARDT. pp. 189-218. IV. Synopsis of the Cretaceous Mammalia of Scandinavia (Norway and Sweden). By W. LILLJEBORG. pp. 219-310. 41 NITZSCH'S Pterylography, translated from the German. Edited by PHILIP LUTLEY SCLATEK. xii + 182 pp., 10 plates. Folio. 1867. For the Twenty -fourth Year, 1867. 42 A Monograph on the Structure and Development of the Shoulder-girdle and Sternum in the Vertebrata. By W. KITCHEN PARKER. xii + 240 + 60 pp., 30 plates. Folio. 1868. 22 PUBLICATIONS OF THE RAY SOCIETY. 43 The Miscellaneous Botanical Works of ROBERT BROWN. [Edited by JOHN J. BENNETT.] Vol. II, containing III, Systematic Memoirs, and IV, Contributions to Systematic Works, viii + 780 pp. 8vo. 1868. For the Twenty-fifth Tear, 1868. 44 Vegetable Teratology, an Account of the Principal Devia- tions from the Usual Structure of Plants. By MAXWELL T. MASTERS. With Numerous Illustrations by E. M. WILLIAMS, xxxviii + 534 pages. 8vo. 1869. 45 The Miscellaneous Botanical Works of ROBERT BROWN. [Edited by JOHN J. BENNETT.] Vol. III. Atlas of Plates, iv + 16 pp., 38 plates. Folio. 1868. For the Twenty-sixth Year, 1869. 46 A Monograph of the Gymnoblastic or Tubularian Hydroids. By GEORGE JAMES ALLMAN. Part I, the Hydroida in General, xxii + 154 + 24 pp., 12 plates. Folio. 1871. For the Twenty -seventh Year, 1870. 47 A Monograph of the Gymnoblastic or Tubularian Hydroids. By GEORGE JAMES ALLMAN. Conclusion of Part I, and Part II, containing descriptions of the Genera and Species of the Gyninoblastea, iv + 2 (xxiii, xxiv) + 296 (155-450) + 22 pp., 11 plates (xiii-xxiii). Folio. 1872. For the Twenty -eighth Year, 1871. 48 Monograph of the Collembola and Thysanura. By Sir JOHN LUBBOCK. x -f 276 pp., 78 plates. Svo. 1873. For the Tic enty -ninth Year, 1872. 49 A Monograph of the British Annelids. By W. C. MclNTOSH. Part I. The Nemertians. xiv + 96 + 20 pp., 10 plates. Folio. 1873. For the Thirtieth Year, 1873. 50 A Monograph of the British Annelids. By W. C. MclNTOSH. Part I continued. The Nemertians. iv + 122 (97-214, 213 a-d) + 26 pp., 13 plates (xi-xxiii). Folio. 1874. For the Thirty -first Year, 1874. 51 A Monograph of the British Spongiadae. By J. S. BOWERBANK. Vol. III. xxviii + 368 pp., 92 plates. 8vo. 1874. PUr.Ll CATIONS OF THE EAY SOCIETY. 23 For flip Thirty-second Tear, 1875. 52 A Monograph of the British Aphides. By GEORGE BOWDLER BOCKTON. Vol. I. x -f 194 + 78 pp., 42 plates (A-C, i-xxxviii, iv his). 8vo. 1876. For the Thirty-third Year, 1876. 53 A Monograph of the Free and Semi-parasitic Copepoda of the British Islands. By G. STEWAEDSON BRADY. Vol. I. iv + us + 72 pp., 36 plates (1-33, 10A, 24A, 24s). 8vo. 1878. For the Thirty-fourth Year, 1877. 54 A Monograph of the British Aphides. By GEORGE BOWDLER BOCKTON. Vol. II. iv + 176 + 100 pp., 50 plates (xxxix— Ixxxvi, li bis, Ixix bis). 8vo. 1879. For the Thirty-fifth Year, 1878. 55 A Monograph of the Free and Semi-parasitic Copepoda of the British Islands. By G. STEWARDSON BRADY. Vol. II. iv + 182 + 98 pp., 49 plates (34-82). Svo. 1880. Fur the Thirty-sixth Year, 1879. 56 A Monograph of the Free and Semi-parasitic Copepoda of the British Islands. By G. STEWARDSON BRADY. Vol. III. iv + 84 + 22 pp., li plates (83-93). Svo. 1880. 57 A Monograph of the British Spongiadae. By the late J. S. BOWERBANK. Vol. IV (Supplementary). Edited, with additions, by the Rev. A. M. NORMAN, xviii + 250 + 34 pp., 17 plates. Svo. 1882. For the Thirty-seventh Year, 1880. 58 A Monograph of the British Aphides. By GEORGE BOWDLER BUCKTON. Vol. III. vi + 142 + 56 pp., 28 plates (Ixxxvii-cxiv). Svo. 1881. For the Thirty-eighth Year, 1881. 59 A Monograph of the British Phytophagous Hymenoptera. By PETER CAMERON. Vol. I. viii + 340 + 42 pp., 21 plates. Svo. 1882. For the Thirty-ninth Year, 1882, 60 A Monograph of the British Aphides. By GEORGE BOWDLER BDCKTON. Vol. IV. x + 228 + 62 pp., 27 plates (D— I, cxv— cxxxiv, cxiv bis). Svo. 1883. 24 PUBLICATIONS OF THE RAY SOCIETY. For the Fortieth Year, 1883. 61 British Oribatida?. By ALBERT D. MICHAEL. Vol. I. xii + 336 + 62 pp., 31 plates (i-xxiv, A-G). 8vo. 1884. * For the Forty-first Year, 1884. 62 A Monograph of the British Phytophagous Hymeiioptera. By PETER CAMERON. Vol. II. vi + 234 + 54 pp., 27 plates. 8vo. 1885. For the Forty-second Year, 1885. 63 The Larva? of the British Butterflies and Moths. By the late WILLIAM BUCKLER, Vol.1. (The Butterflies.) Edited by H. T. STAINTON. xvi + 202 + 34 pp., 17 plates. 8vo. 1886. For the Forty-third Year, 1886. 64 The Larva? of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. II. (The Sphinges or Hawk- moths and part of the Bombyces.) Edited by H. T. STAINTON. xii + 172 + 36 pp., 18 plates (xviii-xxxv). 8vo. 1887. For the Forty -fourth Year, 1887. 65 British Oribatidae. By ALBERT D. MICHAEL. Vol. II. xii + 322 (337-658) + 62 pp., 31 plates (xxv-liv, xlviiA). 8vo. 1888. For the Forty-fifth Year, 1888. 66 The Larva? of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. III. (The concluding por- tion of the Bombyces.) Edited by H. T. STAINTON. xvi + 80 + 36 pp., 18 plates (xxxvi-liii). Svo. 1889. For the Forty-swth Year, 1889. 67 A Monograph of the British Phytophagous Hymenoptera. By PETER CAMERON. Vol. III.' vi + 274 + 34 pp., 17 plates. Svo. 1890. For the Forty-seventh Year, 1890. 68 The Larva? of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. IV. (The first portion of the Noctnae.) Edited by H. T. STAINTON. xii + 116 + 32 pp., 16 plates (liv-lxix). Svo. 1891. PUBLICATIONS OF THE RAY SOCIETY. 25 For the Forty-eighth Year, 1891. 69 The Larvre of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. V. (The second portion of the Noctiue.) Edited (in part) by the late H. T. STAINTON. xii + 90 + 34 pp., 17 plates (Ixx-lxxxvi). 8vo. 1893. For the Forty-ninth Year, 1892. 70 A Monograph of the British Phytophagous Hymenoptera. By PETER CAMERON. Vol. IV. vi + 248 + 38 pp., 19 plates. 8vo. 1893. For the Fiftieth Year, 1893. 71 The Larvae of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. VI. (The third and con- cluding portion of the Noctuae.) Edited by G-EO. T. PORRITT. xii + 142 + 38 pp., 19 plates (Ixxxvii-cv) . 8vo. 1895. For the Fifty-first Year, 1894. 72 The Larvae of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. VII. (The first portion of the Geometrse.) Edited by GTEO. T. PORRITT. xvi + 176 + 44 pp., 22 plates (cvi-cxxvii). 8vo. 1897. For the Fifty-second Year, 1895. 73 The Larvae of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. VIII. (The concluding portion of the Geometraa.) Edited by G-EO. T. PORRITT. xii + 120 + 70 pp., 20 plates (cxxviii-cxlvii). 8vo. 1899. For the Fifty-third Year, 1896. 74 The Tailless Batrachians of Europe. By G. A. BOULENGER. Part I. viii + 210 pp., 10 plates. 8vo. 1897. For the Fifty-fourth Year, 1897. 75 The Tailless Batrachians of Europe. By G. A. BOULENGER. Part II. ii + 166 (211-376) pp., 14 plates (xi-xxiv). 8vo. 1898. For the Fifty-fifth Year, 1898. 76 A Monograph of the British Annelids. By WILLIAM CARMICHAEL MC!NTOSH. Part II. Polychaeta. Amphino- midas to Sigalionidaa. x + 228 (215-442) + 40 pp., 20 plates (xxiv-xlii, xxviA). Folio. 1900. 26 PUBLICATIONS OF THE RAY SOCIETY. For the Fifty-sixth Year, 1899. 77 The Larvae of the British Butterflies and Moths. By the late WILLIAM BUCKLER. Vol. IX. (The Deltoides, Pyrales, Crambites, Tertrices, Tineas, and Pterophori.) Edited by G-EO. T. POEEITT. xviii + 420 + 34 pp., 17 plates (cxlviii- clxiv). 8vo. 1901. For the Fifty-seventh Year, 1900. 78 Monograph of the Coccidaa of the British Isles. By ROBERT NEWSTEAD. Vol. I. xii + 220 + 78 pp., 39 plates (A-E, i-xxxiv). 8vo. 1901. For the Fifty-eighth Year, 1901. 79 British Tyroglyphidse. By ALBERT D. MICHAEL. Vol. I. xvi + 294 + 44 pp., 22 plates (A-C, i-xix). 8vo. 1901. For the Fifty-ninth Year, 1902. 80 Monograph of the Coccidae of the British Isles. By ROBERT NEWSTEAD. Vol. II. viii + 270 + 84 pp., 42 plates (F, xxxv-lxxv). 8vo. 1903. For the Sixtieth Year, 1903. 81 British Tyroglyphidae. By ALBERT D. MICHAEL. Vol. II. xii + 184 + 40 pp., 20 plates (xx-xxxix). 8vo. 1903. For the Sixty-first Year, 1904. 82 A Monograph of the British Desmidiaceas. By W. WEST and Gr. S. WEST. Vol. I. xxxvi + 224 + 64 pp., 32 plates. 8vo. 1904. 83 The British Tunicata. By the late JOSHUA ALDER and the late ALBANY HANCOCK. Edited by JOHN HOPKINSON, with a history of the work by the Rev. A. M. NORMAN. xvi + 148 + 40 pp., 20 plates, and frontispiece. 8vo. 1905. For the Sixty-second Year, 1905. 84 A Monograph of the British Desmidiaceae. By W. WEST and G. S. WEST. Vol. II. x + 206 + 64 pp., 32 plates (xxxiii-lxiv) . 8vo. 1905. 85 The British Freshwater Rhizopoda and Heliozoa. By JAMES CASH, assisted by JOHN HOPKINSON. Vol. I. The Rhizopoda, Part I. x + 150 + 32 pp., 16 plates. 8vo. 1905. PUBLICATIONS OF THE RAY SOCIETY. 27 In Course of Publication. The British Annelids. By Prof. W. C. MC!NTOSH. The British Desmidiaceas. By W. WEST and Prof. Gr. S. WEST. The British Freshwater Rhizopoda and Heliozoa. By JAMES CASH. The British Tunicata. By the late JOSHUA ALDEE and the late ALBANY HANCOCK. Preparing for Publication. The British Centipedes and Millepedes. By WILFEED MAEK WEBB. The British Characeas. By HENEY and JAMES G-EOVES. The British Parasitic Copepoda. By Dr. THOMAS SCOTT and ANDREW SCOTT. The British Sphagnaceze. By E. C. HOEEELL. PRINTED BY ADLARD AND SON, LONDON AND DORKING. • . . . . -.:-..