makcii 1910.] YENDO.— ASEXUAL MODE OF AUXOSPORE. 49 



future trabecular ridge. As the other side of the sporangium 

 remains yet unaltered, general aspect of the spore is a plano- 

 convex. Similar changes take place in the other half soon 

 afterward, and a narrow band of area between both surfaces is 

 now clearly seen as the girdle. The edges become angulate and 

 sharp. The result is a circular disciform auxospore with a 

 narrow girdle band (Fig. 8). The diameter of newly formed 

 frustule measures 370-450/; and is always slightly less than that 

 of the perizonium. The further processes are to execute the 

 trabecular ridges, sculpture, etc., as to fulfill all the characters 

 of an adult individual. 



After the auxospore has been completed the perizonium 

 cracks into two halves more or less along the equatorial line 

 (Fig. 9). The auxospore is thus freed and one thing to be 

 done is to attach to a substratum. But, by what course it 

 reaches to the substratum we can not give exact information 

 at present. 



The matured perizonium is ridged and brittle, rich in 

 silicate. This may be satisfactorily demonstrated by burning 

 a sporangium on mica plate. But before the completion of the 

 shore the membrane seems to be tenacious and elastic, as may 

 well be supposed by an accidentally broken immature sporang- 

 ium (Fig. 10). We have tested the staining reactions of the 

 perizonium as well as of t'.ie pedicellar wall of various stages by 

 using several kinds of reagents. It has been ascertained that the 

 perizonium contained cellulose in a comparatively greater quan- 

 tity while yet young, adding silicate as it grows old ; and that 

 the pedicellar wall consisted chiefly of gelose matter, though an 

 insignificant reaction of cellulose has been observed in the 

 pedicels of young sporangia. (Sapporo, February 1910.) 



Explanation of Plate. Ill 



(All figures are magnified 80 times ; the epitheca 

 are shown diagramatically). 

 Fig. 1. Young sporangium with the hypotheca yet remaining attach- 

 ed. 



