THE SEXUALITY OP THE FUNGI. 63 



association to highly adaptive parasitism, where the fungus has learned 

 (so to speak) to use its host as a slave. 



The most serious objections to the above hypothesis will probably 

 occur to those who draw conclusions from the life-history of imperfectly 

 known forms. Without wishing to disarm auy criticism whatever, I 

 would mention two points to be borne in mind in this connection. 



Many fungi are known to be capable of adapting themselves to 

 widely different modes of life, and it is extremely difficult to say how 

 far they are parasitic or saprophytic. Leaving the Bacteria alone, I 

 need only mention Koch's experiments with species of Mucor and 

 Aspergillus, and Eidam's observations on Sterigmatocystis : l these 

 fungi were found to be pathogenic to a disastrous extent when in- 

 jected into the blood-vessels of living animals. Again, Kihlmann's 

 brilliant research on Melanospora, embodied in an earlier portion of 

 this essay, brings to light an extraordinary case of parasitism and 

 adaptation. 



Secondly, we really know very little of the mode of life of many 

 fungi in their earlier stages ; we assume, rather than knoiv, that many 

 forms of Pyrenomycetes, for instance, are saprophytes. However, less 

 is to be gained by dwelling upon these doubtful matters than by court- 

 ing criticism of the main point at issue. 



I may say, in conclusion, that it was during the study of the 

 parasitic fungus of the Coffee disease {Hemileia vastatrix) in Ceylon 

 that I was first led to speculate on the enormous amount of energy 

 displayed by an organism which shows not the remotest satisfactory 

 trace of sexuality, but which reproduces itself through many genera- 

 tions exclusively by means of asexual spores. That this energy of 

 reproduction is derived from the Coffee tree there can be no doubt, 

 and that it is at the cost of the reproduction of the host is sadly 

 evident ; the clear inference from the fact that the Coffee leaf supplies 

 substance for the reproduction, &c, of a fungus at the expense of its 

 own fruit, is that the fungus takes matters which are very rich in 

 energy, so rich, indeed, that the fungus is not necessitated to sort 

 these substances in special reproductive organs, and to secrete sexual 

 elements, one of which would then re-invigorate the other, but may 

 employ them forthwith for the purposes of its own relatively simpler 

 existence and reproduction. 



i Colm's ' Beiti-age,' B. iii., H. iii., p. 397 fE 



