3<)(5 NOTANrOAL SURVEY OF DISMAL SWAMP REGION. 



Among modifications that arc probably effective in diminishing 

 transpiration may be cited: 



(a) Thickening of the cuticle and epidermis walls, winch is ex- 

 hibited, often to a high degree, by nearly all plants of the salt marsh. 

 This thickening is often conspicuous when species of the salt marsh 

 are compared with nearly related species from other localities, el- 

 even when individuals of the same species, respectively inhabiting 

 the salt marsh and some other habitat, are placed side by side. A 

 more or less pronounced roughening of the cuticle is also frequently 

 to be detected. Its probable service to the plant will be discussed 

 presently. 1 



(b) Hairy covering sufficiently dense to bo of service as a protec- 

 tion again si excessive transpiration occurs only in Borrichia frutes- 

 cens. which has both leaf surfaces very densely covered with two to 

 four celled hairs (each epidermis cell being thus extended by tangen- 

 tial division); on the under leaf surface of Hibiscus moscheutos, and 

 possibly on the stellate-pubescent leaves of Kosteletzkya virginica, 

 in which species, however, the hairiness is far less dense. 



(c) Stomal a, protected by being situated in furrows of the leaf sur- 

 face, which are in some cases partially closed by hairs, in species of 

 Spartina, etc.; and correlated with this — 



((/) Leaf becoming conduplicate or involute, thus concealing the 

 ventral surface, where all or most of the stomatalie, especially in the 

 species of Spartina and in certain sedges. 



(e) Leaf vertical in Juncus roemerianits, Fimbristylis spadicea, and 

 Typha latifolia; nearly vertical in species of Spartina and other 

 grasses, and in Baccharis, Aster spp., Tva frutescens, and other dicoty- 

 ledons with isolateral leaves. 



(/"") Transference of the normal functions of leaves in large part to 

 the (erect) steins, in Juncus roemerianus, Scirpus americanus, and 

 Salicornia herlxtcea. 



(g) Small size of the leaves, and hence of the transpiring surface, 

 without transfer of function to the stems, in Aster subulatus, Aster 

 tenuifolius, Sabbatia gracilis, Lythrum linear?, Lippia sp., Monniera 

 (Herpestis) monniera, and many other species. 



(//) Succulency: of stem (accompanied by reduction of the leaves to 

 mere scales), Salicornia lierbacea; of leaves (moderate), Borrichia, 

 Solidago sempervirens, Aster spp. (in A. subulatus the stems are also 

 somewhat succulent). Succulent plants lose their water much more 

 slowly than do others, since the water tissue, the strong development 

 of which causes the thickening of the succulent parts, gives up its 

 supply reluctantly. This is in some cases due to the presence of a 



1 Page 389. 



