KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 25. N:0 5. 7 



There is another point of eonsiderable influenee upon the existence of Fresh-water 

 Alga 1 , viz. the geological formation of the country; and it is a pity that the eonsequences 

 of this influenee have not received the attention they deserve. I had occasion (Naturalist, 

 Feb. 1886) to refer to these details, and I find that Brebisson (Liste, p. 1 14) agrees with 

 my views so far as a chalky' or cretaceous soil is concerned. Lower Bengal is partly 

 alluvial, partly carboniferous, as regards the earth-strata. 



Wallich states (p. 184 1. c.) that he had observed 140 species of Desmidieaa in the 

 Raneegunge district; to which I may add that this number did not comprise very raany 

 of those I found in his Mscr., in whieh, including sundry doubtful species, there are icons 

 of 238 Desmids. From results obtained by many observera, it appears that the value of 

 gatherings is often in inverse ratio to the extent of country examined, e. g. A. W. Wills, 

 Sutton Park, 89 sp.; idem, Capel Curig and Barmouth, 176 sp.; W. B. T., Strensa.ll Com- 

 mon, near York, över 140 sp.; and Dr. Nordstedt informed me that, in one small Northern 

 habitat, he had obtained 97 species; all being of Desmids. In Mr. Joshuas Burraese Des- 

 midiea 1 ', 1885, also collected within a very small space, appear 186 species and varieties 

 of Desmidicas Lagerhei.m in his 'Desmidiaceen aus Bengalen' 1887, gives 52 species and 

 vars. of the same order. Both these gentlemen give forms not seen by Wallich or my- 

 self; those of Mr. Joshua being (Sphce. pulchrum, Bail. ft trilobum, n. v.; Desm. qua- 

 drangulatum, Ralfs; D. quadratum, Nordst.; Micras. crenata, Breb.; M. apiculata, Ehr. f.. 

 M. ceratophora, ejus; M. euastroides, n. sp.; Euastrum ansatum v. ampliatum; E. binale 

 n, f. crassum; E. gemmatum Breb. v. mononcylum Nord.; E. decedens, Reinsch; E. o/>- 

 longum, Grev. f. scrobiculatum, Nordst.; E. sublobatum, Breb.; E. hypoehondrum, Nordst.; 

 E. attemiatum, Wolle; E. retrorsum; E. jiammeum; E. cor alloides; E. truncatum; E. ser- 

 ratum; and E. divergens, spec. nov.; Staurastrum. proboscideum, Breb. v. Javanicum, Nordst.; 

 S. margaritaceum, Ehrb. v. hirtum, Nordst.; S. gracile, forma? ; S. vestitum, Rfs.; S. avi- 

 cula, Breb.. S- Brasiliense, Nordst.; S. horrescens, n. sp. ; S. leptodermum, Ld.; S. granu- 

 latum, Reinsch; S. minusculum; S. bifurcum, ejus ex. p.; S. cyathodes, n. sp.; S. platy- 

 cerum, n. sp.; Xanthidium acanthophorum, Nordst.; X. antilopamm, 2 forms; Arthrodesmus 

 octocornis, Ehrb.; A. arcuatus, and A. apiculatus, sp. nov.; Cosmarium turgidum, Breb.; 

 C. De Baryi, Arch.; C. pulc/ierrimum, Nordst. var.; C. cucurbita, Breb.; C. amamum, 

 Breb.; C. pyramidatum, Breb. var.; C. latum, Breb.; C. reetangulare, Grun.; C. Norim- 

 bergense, Reinsch; C. globosum, Bulnh.; C. sub-tumidum, Nord. v. fi platydesmium, Nord.; 

 C. annulatum, Nag.; C. paehydermum, Lund. />' minus, Nordst.; C. geminatum, Lund.; 

 C. sub-rotundum, Delp.; C. bicardia, Rsch. ; C. undulatum, v. Schm.; C. quadratum, Ralfs; 

 C. pardalis, Cohn. /. minor.; C. botrytis, v. Indicum, n. v.; and 9 n. sp. C. euastron, 

 C. capax, C. diadem a, C. armatum, C. cuneatum, C. spinosum, C. incisum, C. inornatum, 

 and C. exasperatum; Doc. minutum! Naeg!; Docid. baculum, Breb.; and 3 new sp., D. 

 granuliferum, D. annulatum, and D. Burmense; D. verrucosum, Bail. (as D. tesselatum, 

 Josh.); Closterium Lagoense, Nord.; C. striolatum, Ehr.; C. costatum, Cda; C. ensis, Delp.!; 

 C. lineatum, Ehr. /. Sandvicensis, Nord.; C. Ralfsii, Breb.; C. setaceum, Ehr.; C. Venus, 

 Ktz.; C. inter medium, Ralfs; C. incurvum, Breb.; C. porrectum, Nordst., C. subtile, Breb. 

 cum zyg. (? Cfr seq. sub Rhaphidium); and 2 new species, C. bacillum and C. nematodes; 

 Penium margaritaceum, Ehr.; P. spirostriolatum, Barker; P. minutissimum, Nordst.; and 



