11EV. J. M. CROMBIE ON THE ALGO-LICHEN HYPOTHESIS. 265 



contented with leaving these to develop in a natural way, Treub, 

 on their germinating further, tried to cultivate them by the aid 

 of various nutrient fluids *. After protracted experiments, 

 however, he acknowledges that the results obtained were in all 

 cases very unsatisfactory, owing to the spores not rightly ger- 

 minating, or to the presence of moulds, or to the hyphal filaments 

 not becoming fully developed. This has also been the experience 

 of myself, and no doubt of many others who have attempted 

 spore-cultivation (cfr. Nylander " On the Germination of the 

 Spores of Varicella iria," in ' Flora,' 18GS). Indeed, except under 

 the same conditions of exposure to atmospheric and other 

 influences as those under which they grow in nature, it is not 

 possible to cultivate lichens beyond the earliest stages of evolu- 

 tion f. Their vital phenomena being very intermittent, and 

 unlike that of all other plants — now dormant in dry weather, now 

 active in wet, — their subsequent growth, in consequence of this 

 twofold life, is extremely slow, and the formation of the. perfect 

 plant in most cases a long-protracted process. Hence spore- 

 cultures carried on at home, where the conditions referred to 

 cannot be obtained, can hardly lead to any very definite or final 

 results. And this, owing not to any want of co-operation of the 

 requisite algals, as alleged by Schwendenerians, but to the 

 " extreme impatience of situation aud air which is inherent iu 

 the different species; whence it follows that these vegetables 

 immediately perish, where the natal situation and necessary 

 access of air is disturbed " (Njrl., in Pyr. Or. p. 31). 



But another method of culture has been adopted by Schwen- 

 denerians, who, by the process called Synthesis, or rather Sym- 

 biosis (as it has been termed by De Bary), have made various 

 attempts to manufacture lichens by sowing their spores upon 

 certain algals, or presumed algals. Thus, amongst other experi- 

 ments of this kind, Bees sowed the spores of Collema glaucescem 

 upon Nostoc lichenoides (vide Monatsb. K. Akad. der Wissensch. 

 zu Berlin, 1871); Boriiet sowed the spores of Physcia parietina 



* These nutrient fluids were such as had been used by Boussingaulfc for the 

 development of the Mpcoderms and by Pasteur for that of the Mucidtms. No 

 wonder " that the results were very small," since the nutriment of Fungi and 

 of Lichens is totally different in its nature ! 



t Of all recorded experiments in this direction, none have been more, and 

 few as, successful as those of Tulasne (vide ' Memoire sur les Lichens,' 18o2). 



