282 The American Naturalist. [April, 
tradiction to this, as Reinke himself admits, is De Bary’s state- 
ment that the fungus occasions considerable change in the 
host, the alga. Reinke is unable to evade this, but prefers to 
interpret it as an advantageous adaptation due to the synthesis 
of fungus and alga to form a “consortium.” Then, in like 
manner, the increased rapidity of division, and the great dis- 
tension of the cells of an elder leaf, occasioned by the presence 
of ecidial filaments, are adaptations traceable to incipient 
“eonsortism,” if you wish, parasitism, in reality. The mere 
fact that the histogenetic relations of the cells in a tissue are 
not such that continuous multiplication of cell-individuals is 
possible, as is the case with free alge, has no significance. The 
tissue-cell and the free alga exhibit essentially the same bio- 
logical behavior when parasitized. The only difference is 
that, in the one case, cytogenesis fixes a limit, in the other, it 
does not. 
In many cases, moreover, parasitism effects little or no change 
in the tissues. This is notably the case in Erysiphes, in many 
Peronosporacez, and Uredinew. On the other hand, algal cells 
often become so completely involved in hyphal threads that 
division is impossible, when the existence of real parasitism is 
quickly demonstrated. 
The significance of the soridium and of hymenial gonidia is 
regarded by Reinke as very considerable. To me, both, but 
the soridium especially, are mere modifications of the fungus 
due to changed habit, and contingent upon incipient or ad- 
vanced desexualisation. The significance of either, were they 
universally present, would be neither profound, nor otherwise 
inexplicable. The fact that they occur almost wholly among 
forms possessing a thallus of a considerable degree of develop- 
ment, and the fact of their utter absence in the primitive types 
is sufficient proof of their lack of meaning. Of equal weight 
is the presence of lichenin. The elementary condition of our 
knowledge of microchemistry should deter anyone from gen- 
eralizations derived therefrom. Reinke’s statement concern- 
ing the characteristic presence of many chemical substances is 
essentially one of the antiquated arguments of the lichenolog- 
ists, and is scarcely more valid than that one in which, speak- 
