THE SEXUALITY OP THE FUNGI. 61 



begun, and it is remarkable that the apogamy becomes more and more 

 complete as we ascend through the latter. 



It is not pretended that the hypothesis embodied above at once 

 explains all the cases possible, and it will be well to state a few of the 

 greater difficulties at once. The Basidiomycetes I shall not dwell upon, 

 since our knowledge of them is still very imperfect. The few cases of 

 parasitic Basidiomycetes known can hardly be cited as supporting the 

 view adduced ; and if it turns out that all the forms are as utterly 

 devoid of sexuality as Brefeld's Cojwinus, and that no other generation 

 exists than the one now known, it will be difficult or impossible to 

 reconcile the facts, and the coincidences referred to in this essay may 

 have to be accepted as coincidences only. 



Apart from this, the difficulty must suggest itself to many that 

 there are parasitic fungi — such as the Peronosporece — which neverthe- 

 less develop the sexual organs in the condition 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 Ustilaginece. 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 fermenting sap, and 

 therefore possibly contains far less energy than the substances absorbed 

 by the higher parasitic fungi. There are two other points which may 

 also be of importance. 



The Peronosporece are almost certainly descended directly from Algee 

 which had already won and established strongly marked sexuality. 

 This would probably be lost only after a long time; 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 

 Peronosporece. De Bary l 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 Phytophthora infestans (the 



£ 'Beitr.,' iv, p. 72* 



