220 



Chlorophycece 



Grintzesco 1 has shown that remarkable malformations of 

 Scenedesmus obliquus can be produced by cultures in a nutritive 

 medium of agar and glucose, and that this Alga possesses the 

 physiological property of liquefying gelatine. He finds a Dacty- 

 lococcus-st&ge equivalent to Nageli's D. infusionum, and he 

 attributes the extensive geographical distribution of this plant to 

 the ease with which it adapts itself to different media and different 

 temperatures. 





au.t. 



Fig. 92. A, Scenedesmus obliquus (Turp.) Kiitz. , from Bradford, W. Yorks. B, the 

 state of S. obliquus known as D/ictylococcus infusionum Nag., from Bowness, 

 Westmoreland. C, S. bijiu/atiis (Turp.) Kiitz., from various localities. D P, 

 ,S. <inadriciintlii (Turp.) Breb., from Bradford, W. Yorks. G, S. quadricauda 

 var. horridu* Kirchn., from S.E. Surrey. H, S. quadricauda var. maximus 

 W. & G. S. West, from Pilmoor, N. Yorks. I K, S. denticulatus Lagerh. var. 

 linear is Hansg. ; I and J, from Westmoreland ; K, from Mayo, Ireland. L, S. spi- 

 catus W. & G. S. West, from Saltburn, N. Yorks. (All x 520.) aut, autocolonies. 



There are about 10 British species, of which S. quadricauda (Turp.) Breb. 

 (fig. 92 D F), S. bijugatus (Turp.) Kiitz. ( = 8. obtusus Meyen ; fig. 92 C) and 

 S. obliquus (Turp.) Kiitz. ( = S. acutus Meyen ; fig. 92 A and B) are general and 

 abundant. All three species vary much in size and also in general characters ; 

 they are regular constituents of the freshwater plankton, but occur most 

 abundantly in stagnant water, especially in association with Pediastrum 

 Boryanum, Coelastrum sphcericum, etc. The cells of the largest forms of 

 S. quadricauda reach a length of 30 /u and a breadth of 14 p. S. denticulatus 



1 Grintzesco, 'Recherch. Experiment, sur la Morph. et la Phys. de Scenedesmus 

 Bull, de 1'Herb. Boissier, 2me. ser. 1902. 



