tare 
(te strane eee 
1907] HOLM—RUBIACEAE 177 
The stem.—The basal internodes are four-winged, and very hairy 
from long, unicellular hairs with the cuticle minutely granular 
(fig. 24); otherwise the cuticle is thick and perfectly smooth. A 
very pronounced thickening with layerings is observable in the outer 
cell wall of epidermis, the stomata are raised a little above the 
adjoining epidermis, and the air chamber is deep but narrow. A 
broad strand of about six layers of very thick-walled collenchyma 
is located in each of the four wings, just beneath epidermis. Viewed 
in longitudinal sections the cells of this collenchyma showed the 
cross walls horizontal to very oblique. The cortex consists of about 
seven strata inside the wings and of only three between them; it is 
thin-walled and quite open on account of the very wide intercellular 
spaces; cells with raphides are frequent in this parenchyma, but no 
starch was observed. The innermost layer is differentiated as a 
thin-walled endodermis, directly bordering on a continuous zone of 
leptome, inside of which is a very broad zone of hadrome with the 
vessels narrow and thick-walled. The center of the stem is occupied 
by a thin-walled pith, mostly broken down in the middle. This 
same structure was observed also in the internodes of the mature 
stems, but not in the lateral axes that bear the inflorescences. In 
these the wings are less distinct and the pith is solid. Finally, in 
the floral peduncle the outline is cylindric and the collenchyma totally 
absent. 
The leaves.—An isolateral structure is characteristic of the coty- 
ledons. The lateral cell walls of the epidermis are undulate on both 
faces, and stomata occur on the dorsal as well as on the ventral face. 
The chlorenchyma is represented by a homogeneous tissue through- 
out, of cells more or less oblong to roundish in transverse section, 
and no palisades were observed. Several of the epidermal cells con- 
tained brown, amorphous clumps of resin, and these secretory cells 
in the cotyledons did not differ from the other cells of epidermis. 
The slender petiole has only one broad mestome bundle in the middle 
and no mechanical tissue. 
The small stem leaves and the foliaceous stipules show the follow- 
ing structure. The cuticle is smooth except above the large epidermal 
cells which contain resin, where it is irregularly thickened so as to 
form striations (fig. 25). Viewed en face the lateral walls of the 
