Algae. 405 



it he describes the growth of certain species and the production of 

 various distinct and degenerate forms. He finds that about ninety 

 per cent of the so-called species are merely Polymorphie forms of 

 the other ten; and that it is only by tracing out their life-histories 

 through the Observation of transition-forms, that the specific con- 

 nection of their innumerable variations can be established. Thus it 

 is necessary to stud}^ the Desmidiaceae on the spot, by comparison 

 of the contents of repeated gatherings from the same habitat, and 

 this the author has done for the last fifteen years, thus arriving at 

 the results described in this and his previous papers. The polymor- 

 phism of Docidium trabecula (Ehr.) is discussed and the various 

 forms of that plant are described. Notes are also given on Cosma- 

 rium rectangulnre Grün, and other species of Desmids, with their 

 numerous varieties and forms. Figures are given illustrating the 

 growth of spines and processes in Docidium and Staurastrum. 



E. S. Gepp. 



Welsford, E. J., The Morphology of Trichodiscus elegatis, 

 Gen. et sp. nov. (Ann. Bot. XXVI. p. 239—242. taf. 27. 1912.) 



An alga was obtained on the sides of a glass jar containing 

 Asolla Carolina, which the author considers as the type of a new 

 genus. The Asolla was imported from North Carolina which 

 would therefore appear to be the original home of the alga The 

 alga was eultivated on cover-glasses and its general strueture and 

 reproduetion worked out. It is an epiphyte belonging to the Chaeto- 

 phoraceae, being closely allied to Chaetonema, Endoclonium , and 

 Pseudochaete, and is described under the name of Trichodiscus 

 elegans gen. et sp. n. 



The diagnosis of the genus is as follows: 



Trichodiscus, Welsford. Thallus parvus, epiphyticus, matrici 

 arete adpressus, discum pseudoparenehymaticum e filamentis radi- 

 antibus ramosis inter sese coalitis, ad marginem autem liberis, con- 

 stitutum efformans, ramis erectis brevibus numerosis et pilis longis- 

 simis septatis ornatus; cellulae uninucleatae chromatophoro singulo 

 parietali lobato et pyrenoideo singulo praeditae. Reproductio per 

 zoosporas, per isogametes biciliatas, per aplanosporas, et per cellu- 

 larum palmelloidearum massulas. 



It was found that under the conditions of environment in which 

 the alga was grown, both sexual and asexual reproduetion oecurred 

 simultaneously. G. S. West. 



West, G. S., Algological Notes. V— IX. (Journ. Bot. p. 79-89. 

 6 figs. March, 1912.) 



V. A Diatomaceous Earth from near Choma, in North-west 

 Rhodesia, consisted of a freshwater deposit of recent origin in 

 which the dominant species was Epithemia Argus. Less conspieuous, 

 but almost equally numerous, were Rhopalodia gibberula var. 

 rupestris and R. gibberula var. Schweinfurthii. These diatoms were 

 contained in a matrix consisting of about nine other species. 



VI. A note on 15 species of African Algae. Sphinctosiphon poly- 

 morphus G. S. West (1907) is shown to be identieal with Microcystis 

 ochracea (Brand) Forti. It is pointed out that Crucigenia emarginata, 

 which is only known from Madagascar, is included in Migula's 

 "Kryptogamenfl. von Deutschi., Oesterr., und der Schweiz" owing to 

 defective information given by Chodat in his "Algues Vertes de 



