TISSUES. 283 



strikingly so than in the sand strand, because of the lack, of hirge 

 woody j)lants; and the thickened leaf is usually of a soft, succulent 

 character rather than leathery. A majority of the species show a 

 conspicuously thickened cuticle, which is strongly wrinkl«Ml in 7 out 

 of 15 of them and granular or warty in 3 more. 



Corresponding to the isolateral structure of most of tlu- Icax <-s we 

 find stomata on both surfaces in 12 si^ecies; on tho whohi circumfe'r- 

 ence of the terete leaf of Ju)icusroeinerin?ii(.s; confined to tlie ventral 

 or upper surface only in SjKiriina stricfa und BorrirliUt frufescens. 

 In 4 species the guard cells are slightly prominent, in 7 level with tlie 

 epidermis, in 3 slightly sunken, in 1 {Spariirta slricta) situated in*ar 

 the bottom of deep furrows. Hairs occur in l)ut 5 species. In l5or- 

 richia alone they form a dense covering, nearly every epidermal cell 

 appearing to have developed a iDluricellular, thin-walled liair by 

 tangential division. It is evident that we have in this case an admi- 

 rable j)rotection against excessive transpiration. 



Stereome occurs in notable quantity only in the leaves of SiKiriina 

 stricta and Juncus roemerianus. In both it is subepidermal as well 

 as about the mestome bundles. Juncus roemerianus is especially 

 noteworthy for the strong development of both peripheral and axial 

 stereome groups. Ilj'podermal collenchyma, or collenchyma-likc 

 tissue, occurs opposite the veins in two-thirds of the species examined. 



The chlorenchyma is homogeneous in all but '2 species, and in 1 of 

 these, Lippia nodiflora, the differentiation is slight. In nearly all 

 the si)ecies it consists of comj)acu palisade, interrui)ted in several 

 cases by ducts or lacunes. In the leaves of most of the species there 

 are only 2 layers on each side of the isolateral leaf, but in Ju7irus 

 roemerianus the bands of Avell-developed palisade are 5 or 6 layers 

 thick. In several of the Comj)ositae, all decidedly halophilous species, 

 the ends of the palisade layers where they abut upon the midvein 

 converge toward the vein and appear as if radiating from it. This 

 was observed in Iva frufescens, Baccharis halitnifolia, and Aster 

 teiiuifolius, and may occur in other species. The significance of this 

 arrangement is not known. It is cited by Warming^ as a lialophytic 

 character. SjKirtijia stricta agrees in the arrangement of its chlo- 

 rophyll tissue, as in other respects, with the sand-strand grasses. 



Colorless parenchjnna, which i^robably serves for the storage of 

 water, is present in greater or less quantity in S species, occupying 

 the greater part of the interior of the leaf in 4, while occurring only 

 about the veins in the others. In l>oiricliia, which is one of the most 

 xerophytic in structure of all the salt-marsh species, this tissue is 

 best developed. It is also well exemplified in 'Tissa marina. 



In the 3 salt-marsh inhabiting monocotyledons examined — Triylo- 

 cliin striata, Sjoartina stricta, and Juncus roemerianus — each mes- 



' Halofyt-Stndier, p. S50. 



