1903-1904-] A Short Talk on Lichens. 89 



lap, and so it is here. The genus Endocarpon may be re- 

 garded as a connecting-link with the Hepaticse, and has fruit 

 embedded in the thallus like Eiccias, and Lichinas and 

 Collemas with the algse. Fries says that lichens have the 

 vegetation of algals and the fruit of fungals. They have a 

 vegetative system containing gonidia and a reproductive 

 system of female thecasporous fruits and male spermogonous 

 organs. De Bary, followed by Scliweudener, some years ago 

 propounded the Schwendenerian theory, which makes lichens 

 a product of the medulla of the lichen — a fungus, taking 

 captive, stimulating, and feeding upon algse — the green 

 gonidia. This theory has been adopted by many eminent 

 botanists, but the principal lichenologists reject it. Dr 

 William Nylander of Paris characterises it as presumptuous, 

 premature, and absurd, and the Eev. J. M. Crombie says : " As 

 to the alleged identity of the lichen hypha with a fungus 

 mycelium, it is to be observed that the two are totally 

 different in their nature. The hyphse of lichens are rigid, 

 elastic, containing lichenine, not becoming putrid by macera- 

 tion, with no faculty of penetrating or involving, while the 

 hyphae of fungi are caducous, soft, flexile, with their walls thin. 

 Hence as there is no algal in the lichen so neither is there any 

 fungus, though there is a parallelism between the fructification 

 of lichens and the asciferous section of fungi." Another 

 author says, " It is well known that parasitic fungi destroy 

 the living organisms upon which they fasten ; and if the 

 assumed parasitic fungus does not destroy its assumed algal 

 host, but, on the contrary, excites it to more active growth and 

 more enlarged production of tissue, then it is clear that it 

 cannot be a fungus but the vegetative tissue of a veritable 

 lichen." There may be some plausibility in this theory as 

 long as observations are confined to such plants as Collemas, 

 but it requires a great amount of credulity to believe that a 

 fungus and an alga would produce a Cladonia, for instance ; 

 yet, on the other hand, it is maintained by Stahl and others 

 that lichens have been obtained synthetically by sowing the 

 spores of fungi upon favourable algal cells, and thus proving 

 their dual nature. This parasitism is without parallel in the 

 animal kingdom or in any other part of the vegetable 

 kingdom. 



