THE SEXUALITY OF THE FUNGI. 59 



the sexual elements, or to sort the substances of which they consist, 

 as it were, this may be of importance. 



It must be allowed that no satisfactory theory exists, however, to 

 account for the gradual disappearance, first of sexuality, and then of 

 even the morphologically represented sexual organs in the fungi ; and 

 any attempt to explain the matter seems to involve more than one 

 vicious assumption. 



The sexual act, however, consisting simply or mainly in the re-invigo- 

 ration of protoplasm by the addition of protoplasm of a different 

 nature (though we do not know the kind or limit of difference) from 

 a distance, it may be that an explanation of what occurs in the fungi 

 is afforded by their mode of life. I have already pointed out that the 

 fungi in which sexual organs seem to be most certainly absent are 

 those which are most highly specialised as parasites. Now, we have 

 every reason to believe, first that parasitism is a matter of degree, and 

 secondly that the most highly specialised form of parasitism consists 

 in directly obtaining those contents of the cells of the host which are 

 chemically most complex, and therefore contain most energy. 



I need not dwell on the degrees of parasitism exemplified by plants 

 which merely rob their hosts of space or moisture, or which have ob- 

 tained a hold so intimate that they break it up and feed on the rotting 

 debris, but may at once pass on to consider a few consequences which 

 follow from the mode of life of those highly specialised parasites which 

 have become so closely adapted to their host, that they exist for a 

 time as all but an organic part of its tissues and substance. 



It can scarcely be doubted that the protoplasm of a higher plant, 

 such as a phanerogam, differs from that of a lower cryptogam in being 

 capable of doing more work ; and that the great advantage derived by 

 a parasitic fungus which has its life so adapted that it can tax the 

 cells of a phanerogamous host plant, is that it obtains its food 

 materials in a condition more nearly approaching that of its own 

 substance, than would be the case if it had to work these materials 

 up from inorganic matters. 



Now it seems not improbable that the protoplasmic substance of a 

 higher phanerogam may contain so much energy, that it can not only 

 supply the vegetative mycelium of a parasitic fungus with all that it 

 requires for its immediate growth, but also suffices to enable that 

 fungus to store up enough energy in its asexual or apogamous spores 



