328 SUMMARY OF CURRENT RESEARCHES RELATING TO 



appended to each name, under which the specimens may be found in 

 the Natural History Museum at Stockholm. Several novelties are 

 described. 



Cultivation of Chlorella vulgaris.*— J. Grintzesco has succeeded 

 in isolating this alga and growing- it in various media, and he describes 

 here his experiments and" the results. After a short introduction, he 

 gives a resume of the previous work on Chlorella and a list of the papers 

 winch he has consulted. Then he deals with the habitat of the species 

 and the best means of isolating it for purposes of cultivation. The 

 development of the alga is described under the headings of "General 

 appearance," " Membrane, chromatophore, pyrenoid, nucleus," and 

 •• Division." The second part of the paper details the experiments made 

 in various media, with the formula of each, and the following are the 

 results: — (1) Agar- or gelatin-media, prepared with inorganic sub- 

 stances, form good cultivating media for Chlorella vulgaris. (2) Glucose 

 always stimulates the development of this alga and its action is not 

 harmful, even if the cultures are prolonged for some time. (8) In 

 media which contain no glucose, C. vulgaris shows a tendency to de- 

 velop at the surface of the substratum ; in media containing glucose 

 development takes place equally throughout all parts of the sub- 

 stratum. (4) Peptone is not a better source of nitrogen than are nitrates. 

 (5) C. vulgaris does not liquefy gelatinous media. 



Grown on porous plates the alga develops more slowly than in agar 

 cultures ; in ordinary sterilised water the development is fairly rapid, 

 and if nutritive salts are added growth increases proportionately within 

 a certain limit. 



As regards light, it was found that the direct rays of the sun are 

 unfavourable, but in electric light the alga grows well and rapidly. 

 In total darkness development takes place more quickly than in full 

 daylight. 



The maximum and minimum of temperature which allow of growth 

 in C. vulgaris are respectively 35° C. and 1'8° C. In vacuum-tubes 

 development is retarded, the colonies being invisible until the twentieth 

 day. 



A comparative table of the physiology of Scenedeswus acutus and 

 Chlorella vulgaris, followed by remarks on the polymorphism of these 

 alga?, complete this paper, which is illustrated by six text figures. 



Cell-membrane of Desmidiacese.f — J. Liitkemuller has made a 

 detailed study of the genera of Desrnidiacea? with the exception of 

 four genera, and on the" strength of his results he divides the family 

 into five groups. These are called the (1) Cosmarium type, (2) Clos- 

 terium type, (8) Penium type, (4) Gonatozygon type, (5) Spirotamia 

 type. These groups are founded entirely on characters connected with 

 the cell-membrane, which in certain types consists of two layers and 

 has an apparatus of pores. The variation in form and position of these 

 pores, when present, constitutes characters in the new systematic treat- 



* Rev. Gen. Bot., xv. (1903) pp. 5-19, 67-82. 



+ Beitr. z. Biolog. d. Pflanz., viii. (1902) pp. 347-414 (3 pis.). See also Bot 

 Centralbl., xcii. (1903) pp. 256-60. • 



