bUTLfeR AND KULKARNI. 239 



exceed 6(V. The wall is thin and smooth and at the free end there 

 is a broad blunt papilla. When mature each sporangium has a 

 single large vacuole lying near the centre, the rest of the cell being 

 filled with dense granular protoplasm (PI. IV, Figs. 1 and 2). Ger- 

 mination may occur within half an hour after sowing in water, up 

 to 20 large zoospores being liberated. The zoospores are more or 

 less bean-shaped, one of the longer sides being convex and the 

 other concave or plane (PI. IV, Fig. 3). Each contains a small 

 pulsating vacuole and two cilia arise near together from the concave 

 or plane side, one projecting in front and the other behind while 

 swimming. After swimming for some time they come to rest, 

 round off, lose the cilia and become surrounded by a cellulose wall. 

 At this period they measure from 10 to 13m in diameter (Raciborski 

 gives the measurement of the swimming spores as 15 to 18 by 9 

 to 12//; Sawada 14 to 18 by 9 to 13//). Germination then occurs 

 by a germ-tube, which may be protruded within half an hour after 

 the zoospore comes to rest or within an hour after the liberation 

 of the zoospore from the sporangium. The germ- tube grows and 

 branches for a time (PI. Ill, Fig. 10) but in water dies without 

 forming any definite mycelium. Raciborski 1 describes a peculiar 

 type of germination in this fungus. The zoospore, after coming 

 to rest, puts out a short tube which swells at the tip to form a sort 

 of secondary sporangium which may continue growth by a hypha 

 or may open to liberate one or two secondary zoospores. This 

 recalls the germination of the zoospores of Pythium diacarpum 2 

 and is to be considered as the physiological equivalent of the process 

 of diplanetism in the Sajrrolegnlacecc. Diplanetism is probably, 

 as suggested by Hartog 3 , an adaptation to secure wider dissemin- 

 ation than could be obtained by the swimming spore alone. 

 During the period of rest between the two stages of activity the 

 spore can be passively carried to a distance by currents of water 

 and can then reach a suitable substratum for further development 



1 loc. cit, p. 10. 



- Butlor, E. J. An account of the genus Pythium and some Chylridiacea. Mem. Dept« 

 of Agric. in [ndia, Mot. Sor., I, No. 5, 1907, p. 81. 



J Eartog, .M. On the Formation and Liberation of the Zoospores in the Saprolegnia, 

 Quart. Journ. of Microscop. Science, N. S., XXVII, 1887, p. 437. 



