506 BOTANICAL SURVEY OF DISMAL SWAMP RKOION. 



Stereome in ;i thin, wide group beneath the leptome and a small 

 group above the hadrome of the midveiu. 



Galium hispidulum Michx. 



Sand Strand formal ion, inhabiting the innermost wooded dunes and 

 the pine woods immediately behind them. 



Leaf thickish, bifacial (fig. 90). 



Epidermis nearly alike on both faces. Cells considerably elongated 

 parallel to the length of the leaf; those of the ventral surface high, 

 radial walls thickish (especially on the ventral surface), strongly 

 undulate; cuticle strongly thickened, especially in the leaf margins, 

 where it greatly exceeds the lumen, wrinkled, raised to a papilla in 

 the center of the outer wall of each cell which is not extended into a 

 hair. 1 ' Stomata few on the ventral surface, very numerous on the 

 dorsal, lying in all directions, level with the surface, each bordered by 

 two (occasionally four) parallel crescent-shaped subsidiary cells, one 

 of which is usually larger, 2 these bordered by three to five (usually five) 

 ordinary cells. Hairs on both surfaces stout, blunt-pointed, curved, 

 unicellular, prickle-like, with a thick, granular cuticle/' Large cells 

 containing resin scattered in the dorsal epidermis 1 (fig. 90, e). 



"'In Rmwartlia cordifnlia virtually every epidermis cell of the upper surface 

 is raised into a small conical point furnished with radiating cuticular striae." 

 Vesque, Ann. Sc. Nat. Bot., ser. 7. vol. 1, p. li)2. 



•'"The stoma [in Rubiaceae] is always accompanied by two lateral cells, which 

 often entirely surround it. I have not encountered a single exception in this 

 respect, and I believe that one can boldly exclude from the family of Rubiaceae 

 every plant of which the stomatal apparatus does not present this configuration." 

 Vesque, loc, cit. , 1SK5. 



"The hairs in Rubiaceae are "very rarely [both] elongated and unicellular." 

 Vesque, loc. cit.. p. 19)3. 



'•The midnerve of the large-lobed leaves of PvnUtgonia laciniatn is armed with 

 short hooked hairs, whose form is probably the result of adaptation to a sort of 

 clambering, which allows the leaves to support themselves on neighboring plants, 

 a method of clambering which one finds greatly developed in several (lalieae 

 (Galium, Asperula. Rubia); with these last plants the hair is reduced to a great 

 curved cell borne at the summit of a more or less considerable emergence.'' Loc. 

 cit., pp. l'J2-li>;5. 



As Galium hispidulum does not support itself upon other plants, its possession 

 of hairs of this type is to be attributed not to adaptation to an existing condition, 

 but to the retention of an inherited character which was formerly useful. 



Hairs almost identical with those of (!. hispidulum occur in Triosteum perfoHa- 

 I inn, as figured by Vesque. loc. cit., t. u,f. .', 



'Radlkofer {Uber Pflanzen mit durchsichtigen punktierten Blattern. p. 319; 

 quoted by Solereder, in Engler's Bot. .Tahrb.. vol . 10, p. 415) found secretion cells in 

 the leaf epidermis of some species of Rubia. Epidermal ce'ls of this type are not 

 common, alt Bough occurring in most Aristolochiaceae (see under Asarum virgini- 

 cuiit), in Monimiai eae, Myrtaceae, and a lew other families. 



