THE SEXUALITY OP THE FUNGI. 55 



substrata, and it has not got over the clumsy habit of destroying its 

 host forthwith. If we compare the highly developed, almost intelli- 

 gent, parasitism of a higher Ascomycete or Uredine with this, it will be 

 understood what I mean by specialised parasitism. Instead of clum- 

 sily destroying its host (like Phytoplitora infestans does the potato), a 

 Puccinia is adapted to live in isolated patches of carefully-sheltered 

 leaf tissue, ramifying in the lacunae filled with oxygenated air and 

 aqueous vapour. Here it taps the cells as they manufacture organised 

 substances in the sunlight, taxing them not too much for their strength, 1 

 and its mycelium keeping near the stomata. Its spores are then pro- 

 truded in centrifugal succession, and shaken off from their advan- 

 tao-eously high position on to other leaves, &c. All such adaptations 

 must imply long periods of descent (and the fungus is therefore much 

 further from the parent stock in the phylogenetic scheme), during 

 which even the strong hereditary tendency to produce sexual organs, 

 &c, might become lost, if such organs for any reason became super- 

 fluous. 



This, however, brings us at once to the last object of the present 

 essay ; and I propose to show that it is probable that the sexuality of 

 the higher fungi has disappeared, because its purpose has been equally 

 well or better attained otherwise than by means of sexual organs. 



Preliminary to this it will be necessary to be quite clear as to what 

 sexual organs and the sexual process essentially are. 



The two points common to all the cases of sexual reproduction 

 which have been directly observed are the following : 



1. A larger or smaller quantity of protoplasmic material passes 

 from one portion (the male organ) of the same or another individual, 

 into the protoplasm contained in another portion (the female organ). 



2. The protoplasm contained in the female organ therefore becomes 

 capable of further development ; either at once, or, more generally, 

 after undergoing a period of rest. 



It is not necessary to quote the numerous cases of observed ana- 

 logies between the sexual reproduction of animals and plants ; but 

 will suffice to note that the essential in the sexual process is always 

 the addition of a portion of protoplasm from the male, to the proto- 

 plasm of the female. 



But this is not all. It is now well established in embryology that 



1 Many Uredinece appear to do no injury at all, unless in large amount and for a long 

 time— i.e. the host can pay the tax easily. 



