Genus Statice as represented at Blakeney Point. /. 271 
The margin of the leaf of the various forms shows very little varia- 
tion, for it is always two cells in thickness ; the cells have very thick walls, 
and the angles between them are filled with a substance which gives the 
reactions of cuticle (Text-fig. 20, B, c). Comparison of Text-fig. 20, A, Band C, 
shows that the margin of the broad-leaved form is thicker than that of the 
narrow-leaved, though otherwise it resembles it, and is different from the 
somewhat blunt margin of bettidifolia. This difference between the broad 
and narrow leaved forms is obviously merely related to the difference in leaf 
thickness. In the broad-leaved form the average thickness of the middle 
region of the leaf blade is 0-464 mm. as com- 
pared with 0 448 mm. in the narrow-leaved. 
The structure of the epidermis shows 
differences in the different forms, not only 
in the thickness of the walls but also in 
the degree of development of the cuticle 
and in its striation. Text-fig. 21 shows 
the structure of a typical epidermal cell 
in each of the forms examined. Com- 
parison of Text-fig. 21, B, C, E and G, 
brings out the fact that in the forms where 
the conditions of life as regards water- 
supply are most severe, viz. in the narrow 
(B) and broad (g) leaved lateral plants, in 
the sand plant (c), and in the experimental 
plant (e), the epidermal cells are larger 
and thick walled, and have a heavy ridged 
cuticle, while a well-marked internal cuticle Text-fig. 20. Transverse section 
• , 11 • . , 1 1 t of the leaf-margin of S. binervosa. 
is piesent as well in the narrow and broad Narrow . leaved form (a), broad-leaved 
leaved plants and in the sand plant, but form (b), and bellidifolia (c) ; 0 cuticle. 
X 2 ~ O 
is absent in the experimental form, where 
the conditions are probably a little more favourable. 
The epidermal cells of the mud form (Text-fig. 21, d) were small, 
heavily cuticularized, and an internal cuticle was also present. Here again 
adequate water-supply is not available for the roots, owing to the difficulty 
of water absorption in the salt soil and the open character of the vegetation, 
which renders the air in the region where the leaves are expanded com- 
paratively dry, and this may account for the epidermal structure. 1 
The Main bank plant (A) shows a markedly thinner cuticle than the 
lateral form, and the internal cuticle is absent. This is possibly in relation 
to the more adequate water-supply which the plant possesses (cf. p. 244). In 
1 A characteristic feature in the leaves of nearly all salt marsh plants is the very slight develop- 
ment of cuticle, possibly largely owing to the fact that their aerial parts are expanded in a distinctly 
humid atmosphere. 
