ON THE SEXUALITY OF THE FUNGI. 307 



typical and perfect for the group to which they belong. I have 

 already referred to the fact that many of these forms are really 

 saprophytes, and that others break down and destroy the tissues 

 of their hosts — clumsily killing their prey and then feeding on 

 the rotten mass — and have pointed out that this is a much less 

 specialised form of parasitism than that of the higher Fungi 

 and Ustilaginese. It is true we do not know much about 

 the nature of the food which these Fungi take from the host ; 

 but there is evidence to show that it is of the nature of fer- 

 menting sap, and therefore possibly contains far less energy 

 than the substances absorbed by the higher parasite Fungi. 

 There are two other points which may also be of importance. 



The Peronosporeee are almost certainly descended directly 

 from Algse which had already won and established strongly- 

 marked sexuality. This would probably be lost only after a long 

 time J for we have every reason to suppose that inherited sexual 

 tendencies are among the last to disappear in the modified 

 descendants of organisms. 



Nevertheless, and this is the second point, the sexuality 

 shows signs of disappearance in extreme members, even within 

 the groups of the Peronosporese. De Bary^ shows that in 

 Phytophthora and Peronospora there is a less evident 

 passage over of protoplasm from the antheridium to the 

 oosphere than in Pythium; and that in some cases, indeed, 

 the quantity passing over is too small to be observed. I will 

 not attempt to lay stress on the coincidence that in Phytoph- 

 thora infestans (the fungus of the potato disease) no sexual 

 act has as yet been discovered. 



Another obvious objection may be raised as follows : The 

 SaprolegnitC are in the main saprophytes, and yet they are 

 said to be advanced towards apogamy — parthenogenetic, at anv 

 rate. The answer may be that they are saprophytic chiefly on 

 animal protoplasm which contains more potential energy 

 than does vegetable protoplasm. At the same time, some 

 Saprolegnise are parasitic on plants, and S. ferax now 

 appears to be parasitic on fish.- 



1 ' Beitr.,' iv, p. 72. ■ Prof. Huxley, loc. cit. 



