620 LECTURE XXII. 



Peronosporeae, that there is no differentiation of the proto- 

 plasmic contents of the oogonium into periplasm and ooplasm, 

 but the whole is employed in the formation of the oospheres. 

 According to de Bary no differentiation takes place in the 

 protoplasm of the pollinodium, whereas Pringsheim asserts 

 that a formation of amoeboid antherozoids takes place in 

 Achlya and Saprolegnia. De Bary has been, in fact, unable 

 to observe any actual sexual process in these plants, even in 

 those cases in which the pollinodium throws out a tube which 

 enters the oogonium, for it appears that the tube remains 

 closed. Pringsheim, on the contrary, maintains that the 

 oospheres are fertilised by the amoeboid antherozoids. There 

 is no doubt that in some cases the oospores are parthenogene- 

 tically developed, for in these cases (e.g. Aphanomyces scaber, 

 Saprolegnia hypogynd) oogonia are developed without polli- 

 nodia in relation with them, and in many cases in which 

 pollinodia are present they put forth no tube into their 

 corresponding oogonia. There is therefore no a priori objec- 

 tion to de Bary's view that the oospores of the Saprolegnieae 

 are always parthenogenetically developed. Assuming the 

 correctness of de Bary's view, we have in the Saprolegnieae an 

 instance of sexual degeneration in the group of the Oomycetes, 

 corresponding to that which is afforded among the Zygo- 

 mycetes by those forms which produce azygospores. 



The genus Monoblepharis, described by Cornu, differs from 

 the foregoing groups of the Oomycetes, and in fact from all 

 other Fungi, in that the protoplasm of the male organ under- 

 goes differentiation into ciliated antherozoids. A single 

 oosphere is formed in the oogonium apparently from the 

 whole of the protoplasm of the organ, and fertilisation is 

 effected by the fusion of an antherozoid, which has entered 

 through the ruptured apex of the oogonium, with the oosphere. 

 We find in this genus a differentiation of the sexual cells 

 which is as well-marked as it is in the higher Green Algae, the 

 Muscineae, or the Pteridophyta. 



We pass now to the Ascomycetes. The simplest form of 

 the sexual process in the plants of this group is that described 

 by Eidam as occurring in Eremascus albus. The sexual organs 



