HYMENOLICHENS 



153 



—b 



recognized its. affinity with Thelephora, a genus of Hymenomycetes. Later 

 Johow^ went to the West Indies and studied the Hymenolichens in their 

 native home. The genera and species described by Johow have been 

 reduced to Cora and Dictyonema ; a new genus Corella has since been added 

 by Wainiol 



Johow found that Cora grew on the mountains usually from looo to 

 2000 ft. above sea-level. As it requires for its 

 development a cool damp climate with strong 

 though indirect illumination, it is found 

 neither in sunny situations nor in the depths 

 of dark woods. It grows most freely in diffuse 

 light, on the lower trunks and branches of 

 trees in open situations, but high up on the 

 stem where the vegetation is more dense. 

 It stands out from the tree like a small thin 

 bracket fungus, one specimen placed above 

 another, with a dimidiate growth similar to 

 that of Polystictus versicolor. Both surfaces 

 are marked by concentric zones which give 

 it an appearance somewhat like Padina Pa- 

 vonia. These zones indicate unequal inter- 

 calary growth both above and below. The 

 whole plant is blue-green when wet, greyish- 

 white when dry, and of a thin membranaceous 

 consistency. 



B. Structure of Thallus 



There is no proper cortex in any of the 

 genera, but in Cora there is a fastigiate 

 branching of the hyphae in parallel lines 

 towards the upper surface; just at the outside 

 they turn and lie in a horizontal direction, 

 and, as the branching becomes more profuse, 

 a rather compact cover is formed. The goni- 

 dia, which consist of blue-green Chroococciis 

 cells, lie at the base of the upward branches 

 and they are surrounded with thin-walled short-celled hyphae closely inter- 

 woven into a kind of cellular tissue. The medulla of loose hyphae passes 

 over to the lower cortex, also of more or less loose filaments. The outermost 

 cells of the latter very frequently grow out into short jagged or crenate 

 processes (Fig. 87). 



'Johow 1884. ^ Wainio 1890. 



i 



Fig. 87. Cora Pavonia Fr. Vertical 

 section of thallus. a, upper cortex ; 

 ^, gonidial layer; c, medulla and 

 lower cortex of crenate cells; d, tuft 

 of fertile hyphae. x 160. e, basidia 

 and spores x 1000 (after Johow). 



