40 A MONTANE EAIN-FOREST. 



well-developed velamen. Epidendrum verrucosum has water-storing 

 leaves and false bulbs, and Liparis elata has water-storing false bulbs 

 and thin leaves, and seldom emerges far from the forest floor. 



In the highest level of the tree-tops the epiphytes are small plants 

 in every case excepting the common tank-epiphyte, Caraguata sinte- 

 tenesii, which also grows in the mid-levels. The small orchids of the 

 tree-tops are all provided with water-storing tissue in their leaves, 

 commonest among them being Lepanthes concinna, Lepanthes triden- 

 tata, Lepanthes concolor, and PleurothalKs sp. The small ferns growing 

 with these orchids are mostly species of Polypodium — Polypodium 

 gramineum, Polypodium marginellum, and Polypodium serrulatum being 

 common. A large white Usnea and a smaller yellow species, together 

 with the basidiomycetous lichen Cora pavonia, are common in the tree- 

 tops, particularly on the Ridges at higher elevations, where they grow 

 with the polster mosses Macromitrium and Sclotheimia. 



To proceed from a Windward Ravine up through Slope forest to a 

 Ridge would bring to view in the lower levels of the forest the same 

 transition in epiphytic vegetation that might be seen by climbing a 

 tall tree in a ravine, except that lichens are not conspicuous in the 

 canopy of the Ravines, and the mid-height epiphytes are often found 

 in favorable spots on the ridges. The importance of a living water- 

 conserving substratum for the occurrence of the mid-height epiphytes 

 is everywhere apparent on the slopes and ridges. 



I have shown in an earlier paper^ something of the comparative 

 power of drought resistance in Stelis ophioglossoides, a typical leaf- 

 storage epiphyte, and Caraguata sintenesii a typical tank-epiphyte 

 (incorrectly designated as Guzmania tricolor in the paper alluded to). 

 When deprived of its catch of water Caraguata exceeded Stelis in its 

 ability to persist in the absence of renewed supplies of water while kept 

 in the laboratory for fifty days. During the longest periods of drought 

 to which these forms are apt to be subjected Caraguata would be 

 exposed to conditions more favorable to water-loss than would Stdis 

 in its mid-height position in the forest, so it is probable that under 

 natural conditions the two types would both meet the hmit of their 

 resistance at the end of six or seven weeks without renewed supplies 

 of water, an extreme condition which the weather records would indi- 

 cate has happened but once in the past thirty-nine years, this occasion 

 being in the vicinity of New Haven Gap in the spring of 1892 (see p. 15). 



With such capacity for drought resistance may be contrasted the 

 character of the most hygrophilous of the filmy-ferns, such as Tricho- 

 manes capillaceum and Trichomanes rigidum, to which the total depriva- 

 tion of water for seventy-two hours is fatal, provided the surfaces of 

 the leaves are dried off at the outset of the period and the humidity 



'Shreve, F. Transpiration and Water Storage in Stelis ophioglossoides. Plant World n- 

 165-172, Aug. 1908. ' ' 



