a 
Se ae 
1907] HOLM—RUBIACEAE 159 
OLDENLANDIA GLOMERATA (HEDYOTIDEAE B. et H.) 
An annual plant and the last of the Rubiaceae to bloom. It 
inhabits wet places on borders of swamps, being associated with 
Hypericum mutilum, Ilysanthes attenuata, Cyperus diandrus, and 
Fimbristylis autumnalis, but is very rare in the District of Columbia. 
The short stem is erect from a decumbent base, and all the leaves, 
which are opposite and short petioled, subtend small cymose inflores- 
cences; the apex of the stem is also terminated by an inflorescence. 
The basal internodes and the hypocotyl soon become bent towards 
the ground, and secondary roots develop freely from the full length 
of the internodes. There are buds in the axils of the cotyledons 
(one at each) which develop into small floral shoots of one or two 
internodes, but so late that their flowers are just beginning to open 
when those of the primary shoot are in fruit. The primary root is 
short, but has many lateral branches. 
The roots.—The main root is hairy and has no exodermis. The 
cortex consists of three strata of very large, thin-walled cells, and the 
endodermis is thin-walled, with the Casparyan spots very distinct. 
The stele showed secondary formations in the leptome and hadrome, 
so that the primitive organization could not be ascertained. The 
lateral and secondary roots, on the other hand, do not increase in 
thickness and remain as diarch. They have long hairs, and show 
the same structure as the primary, but are much thinner. In the 
stele there are two strands of leptome, and the center is sometimes 
occupied by a wide vessel or by a small mass of conjunctive tissue. 
In these capillary roots the endodermis and pericambium are thin- 
walled and continuous. 
The stem.—The hypocotyl is cylindric in contrast with the inter- 
nodes above, which are quadrangular, and is perfectly smooth and 
glabrous. A thin-walled epidermis covers a cortex of three strata 
of very large cells in which raphides occur. The innermost layer is 
differentiated as an endodermis, which consists of small, thin-walled 
cells, surrounding the central cylinder. In this the leptome forms 
a closed ring around the hadrome, of which the rays are quite long, 
separated from each other by narrow medullary rays. A thin-walled 
pith occupies the center of the stele. 
The upper internodes are obtusely quadrangular in cross-section, 
