THE SEXUALITY OP THE FUNGI. 33 



Now a whole series of forms are known leading us up from Podo- 

 sp>hcera and the other Erisyphece through the Pyrenomycetes and Disco- 

 mycetes, and it is remarkable that (apart from some peculiar forms to 

 be referred to shortly) the best investigations lead us to conclude that 

 while the sexual organs are present, but functionless, in the lowest 

 forms, they disappear entirely in the higher Ascomycetes. 



These facts may be put shortly in the form of a diagram as annexed, 

 where attention is only paid to the points referred to. 

 Other Ascomycetes 



I 

 Erysiphese 



Podosphsera 



Other Peronosporece 



Phytophthora 



I 



Pythiurn. 



If we now turn to the Saprolegnice, we may note that De Bary finds 

 that, between the typical cases where the antheridia pierce the oogo- 

 mium wall, but do not empty any protoplasm into the oospheres (Achlya 

 and some Sapirolegnias) and the extreme parthogenetic forms of Sapro- 

 legnia where no antheridia are formed at all, there exist cases where 

 the antheridia apply themselves to the outside of the oogonia, but 

 either form no antheridial tubes at all or only rudimentary ones {S. 

 torulosa, S. asterophora). These facts may also be diagrammatically 



represented as follows. 



Parthenogenetic 

 forms of Saprolegnia 



S. torulosa, 8. Asterophora 



Achlya, Typical 

 Saprolegnia 



Peronosporece. 



If now the various cases are duly considered, De Bary thiuks that 

 we may probably regard the Peronosporeaz as phylogenetically impor- 

 tant in two senses : 



1. Their general biology strongly suggests that they are derived 

 from Algal ancestors, possibly not very unlike Vaucheria and its allies. 



D 



