BEV. J. M. CBOMBIE 03" THE ALGO-LICHEN HYPOTHESIS. 267 



segments certain hyphal filaments which, as they became more 

 evolute, invested the gonidimia, and these, as be says, increased in 

 size owing to the influence of the hyphae, which prevented them 

 from undergoing division. From this hyphal involution, under 

 special circumstances of cultivation, a more or less differentiated 

 thallus at length became apparent, and a lichen was, strange to 

 say, synthetically manufactured out of a lichen-spore and lichen- 

 gonidimia. Here, however, it is but right to notice that in Symbi- 

 osis the spore is " assumed " to be a fungus * and the gonidia to be 

 algals, which, like other assumptions in Schwendenerism, is clearly 

 a " begging of the whole question." Any logical synthesis which 

 could substantiate the hypothesis would evidently be the forma- 

 tion of a lichen by means of the coalition of the filaments of a 

 well-ascertained fungus and an authentic algal. In regard to 

 this, Dr. Lindsay, in a communication against Schwendenerism, 

 which appeared in ' Nature ' for January 27th, 1876, says : — " If, 

 by artificial cultivation, such a union (i. e. of a fungus and alsial) 

 could be made to produce a lichen, the theory might be held as 

 proved " f. Now direct observations made in nature itself have 

 shown me that such contact between the hyphae of a Pyre- 

 nomycetes and a Protococcus, instead of producing anything in 

 the shape of a lichen, is simply destructive to the algal, which 

 the mycelium overruns and involves. Besides, and as is well 

 known to every practical lichenist, in cases where fungal hyphae 

 attack (as they often do) either the epithecium or the hymenium 

 of lichen-apothecia, the texture is at once destroyed and the 

 apothecium is killed by the parasite. Hence, instead of there 

 being any affinity, as presumed, there is a mortal antagonism 

 between a lichen and a fungus, which would at once have become 

 apparent had the Schwendenerians tried to cultivate lichens, 



* The spores of Lichens, notwithstanding a certain similarity, are of a totally 

 different nature from those of Fungi, differing, amongst other characters, in 

 their consistency, in the nature of the hymenial gelatine, and in their producing 

 licheno-hyphaj (yid. infra). Indeed, that the spore of a lichen cannot be a fungal- 

 spore is evident from the fact that several maritime lichens are intertidal, 

 whereas even a short immersion in salt water is destructive alike to the 

 protohypha: and the apothecia of Fungi. 



t By some singular misunderstanding of the subject, Dr. Vines (in Quart. 

 Journ. Micr. Sc. vol. xviii. n. s. p. 153), after quoting these words of Dr. Lind- 

 say, immediately adds, " Such evidence is afforded by Stahl's paper on the 

 nature of hymenial gonidia " ! 



