122 MORPHOLOGY 



easily traced, but when they are orange-coloured, as according to VVainio' 

 they frequently are in Cladonia miniata and CI. digitata, they are more 

 readily observed, especially if the habitat be a mossy one. 



In CI. alpicola it has been found that the rooting structure is frequently 

 as thick as the podetium itself If the podetium originates from the basal 

 portion of the squamule, the hyphae from the chondroid layer, surrounding 

 the hollow centre, take a downward direction and become continuous with 

 the rhizoid. Should the point of insertion be near the apex of the squamule, 

 these hyphae form a nerve within the squamule or along the under surface, 

 and finally also unite with the rhizoid at the base, a form of rooting charac- 

 teristic of CI. cartilaginea, CI. digitata and several other species. 



Mycelium may spread from the rhizinae along the surface of the sub- 

 stratum and give rise to new squamules and new tufts of podetia, a method 

 of reproduction that is of considerable importance in species that are 

 generally sterile and that form no soredia. 



Many species, especially those of the section Cladina, soon lose all 

 connection with the substratum, there being a continual decay of the lower 

 part of the podetia. As apical growth may continue for centuries, the 

 perishing of the base is not to be wondered at. 



G. Haptera 



The presence of haptera in Cladoniae has already been alluded to. They 

 occur usually in the form of cilia or rhizinae''', but differ from* the latter in 

 their more simple regular growth being composed of conglutinate parallel 

 hyphae. They arise on the edges of the squamules or of the scyphus, but 

 in CI. foliacea and CI. ceratophylla they are formed at the points of the 

 podetial branches (more rarely in CI. cervicornis and CI. gracilis). By the aid 

 of these rhizinose haptera the squamule or branch becomes attached to any 

 substance within reach. They also aid in the production of new individuals 

 by anchoring some fragment of the thallus to a support until it has grown 

 to independent existence and has produced new rhizinae or holdfasts. They 

 are a very prominent feature of CI. verticillaris f penicillata in which they 

 form a thick fringe on the edges of the squamules, or frequently grow out 

 as branched cilia from the proliferations on the margins of the scyphus. 



H. Morphology of the Podetium 



In the above account, the podetia have been treated as part of the 

 vegetative thallus, seeing that, partly or entirely, they are assimilative and 

 absorptive organs. This view does not, however, take into account their 

 origin and development, in consideration of which Wainio^ and later Krabbe^ 



1 Wainio 1897. 2 Wainio 1897, p. 9. 3 Wainio i88o. 1 Krabbe 1891. 



