164 BOTANICAL GAZETTE [MARCH 
the upper face of the blade, especially near the apex. Viewed in 
transverse sections the blade shows a typical bifacial structure. The 
epidermis is thin-walled on both faces, but the lumen of the cells is 
considerably wider on the upper than on the lower face; the stomata 
are level with the epidermis. The chlorenchyma is differentiated into 
a palisade tissue of two strata and a pneumatic tissue of four layers; 
the latter tissue is very open and the cells are oblong to almost round- 
ish, with wide intercellular spaces. Neither collenchyma nor stere- 
ome was observed; thus the mestome strands are located directly 
in the chlorenchyma; they are collateral and are surrounded by a 
green parenchyma sheath. The blade thus exhibits a very weak and 
simple structure. 
The petiole is hairy at the base from pluricellular glandular hairs 
(fig. 6), but otherwise it is perfectly glabrous. It is triangular in 
cross-section. The cuticle is somewhat wrinkled, and the epidermis 
consists of large, thin-walled cells. A compact, chlorophyll-bearing 
parenchyma surrounds a single central mestome bundle, which is 
orbicular in transverse section and shows a very distinct, thin-walled 
endodermis. 
The stem leaves are sessile, very narrow, and scabrous along the 
margins from unicellular, prickle-like, and curved projections of the 
epidermis. Glandular hairs (jig. 6) are frequent along the margins 
of the stipules. The epidermis of the upper face shows a very pro- 
nounced striation of the cuticle (jig. 4); the lateral cell walls are undu- 
late on both faces, and stomata with one pair of subsidiary cells were 
observed in equal number on both faces of the blade. While the 
cuticular striations appear as radiating from the center of the epi- 
dermal cells on the upper face, the striae on the lower face are parallel 
with the longitudinal axis of the leaf. In transverse sections the outer 
cell wall of the epidermis is moderately thickened and shows the 
elevated cuticle very distinct on the upper face (jig. 3). Otherwise 
the structure is identical with that of the basal leaves and shows the 
absence of mechanical tissues; the chlorenchyma, however, is less 
developed, there being only one layer of palisades, and the pneu- 
matic tissue is composed of very irregularly shaped cells with wider 
intercellular spaces and contains raphides. 
The characteristics of H. coerulea, therefore, are the lack of col- 
mete 
