490 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and gives their synonyms. The first form, f . simplex, is not the most 

 common, but is tlie one from which all the others spring and is the only- 

 one which is found in an unmixed state by itself. All the forms have 

 the same cell structure and react in the same manner to coloration. 

 They therefore belong genetically together. Under favourable circum- 

 stances the above alga possesses unlimited growth and is perennial. 

 Active reproductive cells were not seen. Spontaneous cutting-off of 

 one or many-celled portions of thallus occurs often. The reproductive 

 akiuetaj need more study. 



Bavarian Desmids.*- — R. Gistl writes on the Desmid flora of the 

 Bavarian upland swamps. For the five districts examined, 115 species 

 are recorded, of which forty are new to Bavaria. Oue of these is new 

 to science, Nectrium coniciim ; and a new variety is described for 

 N. ohlongnm. Details of size are given for each species, based on 

 original measurements. As regards the biology and methods of culture, 

 nothing new is given. Certain species, such as Cosmarivm compressum, 

 which remained dry for eighteen months, seem to be insensitive to 

 outward conditions. Four species sustained life through six months in 

 a dry state, Cosmarhim siihagnicoJum, Euastrum scrobiculare, Micrasterias 

 trimcata, and Staurastrum manjaritaceum. Closterium pronwn and 

 Tetmemorus Isevis are resistant to cold. Both survived being frozen in 

 ice. It is therefore possible that those species, for which zygospores are 

 unknown, do not possess them because they are capable of resisting 

 drought and frost. 



Diatoms of Brazil. f — C. Zimmerman continues his studies on the 

 diatoms of Brazil. In the present note he records 121 species belonging 

 to forty-seven genera. 



Fossil Algae. I — C. D. Walcott writes on the Pre-Cambrian Algon- 

 kian Algal Flora. The first part contains general considerations on 

 continental conditions during Algonkian time ; the origin of Algonkian 

 limestones ; the deposition of limestone through the agency of algte, 

 magnesian limestones, and the algal flora. In the latter chapter a com- 

 parison is made between recent blue-green algte deposits and those of 

 Algonkian time. Special attention is directed to the resemblance of 

 some of the fossils and the so-called lake-balls. A large number of new 

 genera and species are described and illustrated. In one of these, 

 Camasia, chains of microscopic cells were obtained by treatment with 

 hydrochloric acid. The chains resemble Cyanophycefe. The one species 

 described comes from the Newland limestone, Meagher County, Montana, 

 and is unusually interesting owing to its resemblance to the deposit 

 made by the Cyanophycea? in the fresh-water lakes of New York, 

 Michigan, and elsewhere. 



* Beitr. z. Kenntn. d. Desmidiaceenflora der Bayerischen Hochmoore. Miinchen 

 (1914) 60 pp. (4 pis.). See also Bot. Centralbl., cxxxi. (1916) p. 653. 



t Broteria, xiii. (1915). See also Bot. Centralbl., cxxxi. (1916) p. 567. 



X Smithsou. Miscell. Coll., Ixiv. (1914) pt. 2, pp. 77-156 (pis. 4-23). See also 

 Bot. Centralbl., cxxxi. (1916) pp. 651-3. 



