232 THE JOURNAL OF BOTANY 



small and densely tufted, and the tufts are frequently sunk in 

 crevices of the rock or ground which they completely fill, allowing 

 little purchase to the wind. The leaves are frequently very 

 hygroscopic, as in chomophytic species, in wet weather open, 

 in drought closely appressed and imhricate. The stunted growth, 

 often attained by a shortening of the internodes, brings the leaves 

 closer together, so that when appressed their apices alone are 

 exposed. The cells are usually small, thick-walled, and often the 

 thickness is increased externally by papillae. This seems to be 

 especially the case with mosses having comparatively blunt leaves. 

 These papillae probably act, like the apices of the leaves, as foci 

 on which moisture condenses during cloud-fog. The Lichens, 

 also, are usually diminutive in size, or, if of larger growth, more 

 or less compact and cushion-like. The only Cladonia noted was 

 a small form of C. cervicornis, in which the thallus was reduced 

 to a dense squamulose cushion, and the podetia very diminutive. 

 Stereocaulon and Spliaropliorus occur in very compact forms, the 

 outer stems prostrate, the next inclined, the central ones erect, so 

 that the points only are exposed, and no lateral stress is received 

 in wind-storms. The only foliose Parmclia seen was the closely 

 appressed P. alpicola, which is so reduced as to resemble a 

 crustose Lecanora. The laciniae of the thallus are very convex, 

 imbricate and complicate, and often torulose, so that when wetted 

 the water is partly retained in the very numerous depressions 

 thus formed in the thallus, and such as finds its way under the 

 subtubular divisions is retained. The tough leathery Gyrophor(B 

 are centrally affixed, and often depressed at the margins, forming 

 shields beneath which moisture is retained longer than on the 

 open rock. In the case of G. torrefacta the under side is often 

 fibrillose and covered with several trabeculate membranes, the 

 whole producing a sponge-like texture. Occasional perforations 

 admit moisture under the thallus. Lecanora tartarea assumes a 

 very different appearance from that which it presents on trees or 

 rocks at lower altitudes. It creeps over mosses and plant-roots, 

 giving off at intervals slender spinulose processes, w'hich no doubt 

 act as dew-collecting points. The erect fruticose lichens, so 

 plentiful in the next group, are almost absent. They are repre- 

 sented by Parmelia lanata, a decumbent or prostrate appressed 

 plant with the appearance of Alcctoria nigricans, but a totally 

 different habitat and mode of growth ; and Thamnolia vcrmicu- 

 laris, a prostrate plant which hardly leaves the ground except 

 where it turns up its pointed ends as an attraction to the dew. 

 Many of the Lccidece. have large fruits, and very little thallus. 

 The hyphae ramify in minute interstices of the stone, and the 

 gonidia cluster under the lee of their own apothecia, so that they 

 often at first sight appear to be quite athalline. This is especially 

 the case on loose stones of small size, where the conditions are 

 intensely dry. 



Like the scouts of an army, these outposts of vegetable life 

 lead a precarious existence, and they take " cover " behind any 

 prominent object, especially on the leeward side. Their growth 



