 LICHENS. 75 



that no li'chenologlst of any repute, and no mycolo- 

 gist of any authority, supported the theorists during 

 the controversy, but rejected their views as untenable. 

 This is important, as an historical fact, since these 

 were just the scientific men who were practically the 

 best acquainted with the organisms in question, and 

 whose judgment would have the greatest weight. 

 Lichens consist, normally, of a thallus, or vegetative 

 system, which in many species is a tough coriaceous 

 expansion, horizontal or vertical, attached at the base 

 for its support to rocks, stones, wood, and other sub- 

 stances, but not deriving sustenance from the object 

 to which it is attached. In the interior of this thallus 

 minute green bodies, or cellules, form a sub-cortical 

 layer, which are denominated gonidia, and which Dr. 

 Nylander, a most eminent lichenologist, says, " consti- 

 tute a normal organic system, necessary and of the 

 greatest physiological importance, so that around 

 them we behold the growing (or vegetative) life 

 chiefly promoted and active." In addition to these 

 is the reproductive system, which consists of apo- 

 thecia, or discs, borne upon the thallus, containing the 

 asci and sporidia, or reproductive organs. Such are 

 the organisms which have been called lichens, and 

 are regarded by the best scientific authorities as com- 

 plete and autonomous plants, equally with fungi and 

 algae, amongst the lower cryptogamia. On the other 

 hand, the theorists contended that the thallus and 

 reproductive system were, not only fungoid in cha- 

 racter, but absolute fungi, whilst the green gonidic 

 layer of cellules were simply unicellular algae, upon 

 which the fungus was parasitic. Hence the lichens 



