BOTANICAL GAZETTE. 145 



in the Fungi is afforded by their mode of life. The Fungi in 

 which sexual organs seem to be most certainly absent are those 

 which a're most highly specialized as parasites. Now, we have 

 every reason to believe, first, that parasitism is a matter of de- 

 gree, and secondly, that the most highly specialized form of par- 

 asitism 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 obtained 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 crypto- 

 gam 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 contains 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 to last until the next generation of the fungus 

 gains its holdfast on another (and it may be distant) source of life- 

 giving substance. 



Let us take the case of a uredinous fungus parasitic in the 

 leaves of a phanerogam. We know that the substances necessary 

 for the whole growth of the phanerogam are formed in the cells 

 of the leaf; not only so, the matters which eventually find their 

 place in the reproductive organs must be formed there also, po- 

 tentially at least. The leaf of a phanerogam so attacked, more- 

 over, is able to support the parasitic fungus for a long time un- 

 injured, as I have convinced myself by experiment, and there can 

 be no doubt that substances pass into the fungus which would 

 normally have passed into other parts of the host plant itself. 



But we may imagine even this to fail after a time — we may 



