132 PRINGSHEIM, ON THE IMPREGNATION 



smaller than in Vauchcria, and it i-ppresents an oval, sliar])lv- 

 defincd slit (fig. 27). 



The passage for the spermatozoids into the parent-cell of 

 the quiescent spore of Bulhocka'te is formed in a different 

 way ; in this instance the membrane of the sporangium, like- 

 wise in consequence of the accumulation of its contents, is 

 also ruptured ; but in a transverse fissure, more or less above 

 the middle (figs. 28, 29), so that the membrane is split into 

 two perfectly separate parts, between which the open passage 

 to the contents of the sporangium is rendered possible. 



The openings of the sporangia in CEdogonium, and the trans- 

 verse fissures of those in Bulbochate, both of which afford an 

 open passage into the interior of the sporangium, being thus 

 made known, a phenomenon common to both plants demands 

 the closest consideration. 



Besides zoospores and quiescent spores, a third kind of 

 spores are met with in these plants, which are formed in 

 smaller cells, widely different from the common vegetative 

 cells (fig. 30a). To this kind of spore A. Braun has applied 

 the name of " mic?'ogonidia,'^ noticing, at the same time, 

 that the product of their germination is merely very minute, 

 usually bicellular little plants. These microgonidia, which 

 present precisely the same structure as the zoospores, always 

 affix themselves in a remarkable way, either upon the 

 sporangium or close to it. In CEdogoiiium they are found 

 seated sometimes upon the membrane of the sporangium, some- 

 times upon that of the cell immediately contiguous to it, and 

 in Bulboc/i(Bte invariably upon the sporangium (figs. 28, 29, 30). 

 Hence they open, either at once or after they have pushed 

 out one or two short cells, and pour out their contents. 

 Although, at present, no indication of spermatozoids has 

 been observed in them, still the remarkable concurrence of 

 the evacuation of these microgonidia, immediately over, or 

 at any rate very close to the opening of the sporangium in 

 (Edogonium and of the transverse Jissures in Bulbochcete 

 necessarily leads to the supposition that the contents of the 

 microgonidia penetrate into the sporangia, and the author 

 has no doubt that it will be found that the impregnating 

 morphological elements of CEdogonium and Bulbochcete 

 exist in the little plants produced from the microgonidia. 

 But this impregnation in Bulbochcete and QLdogonium differs 

 essentially from that which is observed in Vaucheria, for in 

 the former case the two kinds of sexual organs are not pro- 

 duced upon the fully developed plants, but a special struc- 

 ture, a prothallus as it were, simply bearing antheridia is 



