POPULAR HISTORY OP LICHENS. 



same may be said, though in a minor degree, of the vario- 

 larioid form. The pillar or cone-like bodies constituting the 

 isidioid thallus are frequently dark or coloured at their 

 apices; these were supposed by the older authors to be 

 apothecia, to which, from their form, they gave the name 

 globuli. The soredic and isidioid conditions are sometimes 

 combined in the production of fruticulose, powdery masses 

 termed glomeruli, which frequently occur on the thallus of 

 Parmelia amplissima and Umbilicaria jpustulata. 



The thallus is developed from and upon a rudimentary 

 body termed the hypotliallus ; to understand the proper 

 relations and importance of which, it will be advisable to 

 glance briefly at the progressive development of a Lichen- 

 thallus from the germination of a Lichen-spore. In germi- 

 nating, under favourable circumstances with regard to mois- 

 ture, light, heat, etc., the spore, or cellular embryo of a Li- 

 chen, sends forth usually from one, sometimes from both of 

 its extremities, and occasionally from all points of its surface, 

 delicate filaments or tubes which gradually become elongated 

 and branched, spreading upon, or piercing, to various de- 

 grees, the base of support, — -the ramifications, intertwining so 

 as to form a loose, felted texture, resembling closely, in ge- 

 neral characters, the mycelium of Fungi. This network of 



