REV. J. M. CK0MB1E ON THE AL GO-LICHEN HYPOTHESIS. 2G9 



certain sense analogous to the parasitism involved in this theory. 

 Such entophytic algals, however, are evidently veritable parasites, 

 and prove nothing as to any algo-fungal parasitism in the lichen. 

 It has, also, more recently been alleged (though surely not 

 seriously !) that Schwendenerism has received a certain kind of 

 support from the supposed existence of some unicellular Algae, 

 ZoocHorella and Zooxanthella, as they have been termed, which 

 occur as parasites in some families of Zoophytes, and which, 

 nourished at the expense of the protoplasm of their hosts, at the 

 same time contribute to the synthetical formation of the organic 

 substances utilized by these inferior animals. But these chloro- 

 phylloid bodies have not yet been proved to be true Algae, and 

 even if they were so, there would be no analogy whatever be- 

 tween such parasitism and that of the Algo-lichen theory. 



Reverting, therefore, to Schwendenerism, and granting that 

 the presumed slave not only feeds its master, but also in doing 

 so flourishes and multiplies all the more, " TJpon what," as Mr. 

 Bentham so pertinently asks (Anniv. Address, Linn. Soc. 1872, 

 p. 28), " do the gonidia themselves feed ? " This is a very im- 

 portant point in the physiology of Lichens, which Schwendenerism 

 cannot satisfactorily explain. Detained in a dark and narrow 

 prison, and deprived of the free life they formerly led by the 

 tyrant who has surrounded and enclosed them in his meshes, 

 they are evidently cut off from all communication with that outer 

 world, from which they could receive such nourishment as they 

 themselves require, and the much larger quantity their master 

 exacts from them. "Whence, then, and how is this nutriment 

 derived ? Now it is a well-established fact that lichens obtain 

 their whole nourishment from water, with the different ingre- 

 dients contained in it and necessary for their existence, accord- 

 ing as that water comes from the clouds, from dew, from rivers 

 and lakes, or from the sea. It has sometimes indeed been 

 affirmed (and distinctly so by Sehwendener) that the nutriment of 

 lichens is also partly furnished by means of the substratum. 

 This, however, is a mistake, for, as experiment shows, they thus 

 derive nothing, and, in the case of crustaceous species, evidently 

 can derive nothing in the shape of nutrition (cfr. Nyl. in ' Flora,' 

 1874, p. GO). Anything that they can in this way derive is simply 

 through immixtion with their elements of certain particles, 

 such as iron and chalk, dissolved by the water which is poured 

 forth around them and mechanically received. Their true nutri- 

 ment, derived, as we have said, from water, chiefly rain-water, is 



