1907] HOLM—RUBIACEAE 155 
some service; and the writer is under the impression that a detailed 
account of a few plants, hitherto left unstudied, may prove more 
useful than a broad anatomical treatment of a number of genera and 
species more or less vaguely described or insufficiently compared. 
Among the North American plants that have not been studied 
fully thus far are the Rubiaceae, at least the genera enumerated in 
the title of this paper. With the object of presenting a contribution 
to the knowledge of some of these plants, the writer has endeavored 
to gather as many data as possible from the vegetative organs which 
may be of some interest to students of plant anatomy. The follow- 
ing species have been studied: 
Cephalanthus occidentalis L. (swamps near Brookland, D. C.), Oldenlandia 
glomerata Michx. (swamp near Brookland, D. C.), Houstonia coerulea L. (open 
thickets, D. C.), H. purpurea L. (with the preceding), Mitchella repens L. 
(wooded ravines near Sligo, D. C.), Diodia teres Walt. (open fields, Brookland, 
D. C.), Galium pilosum Ait. (thickets, Brookland, D. C.), G. triflorum Michx. 
(woods near Anacostia, and on the Potomac shore, Va.), G. circaezans Michx. 
(with the preceding), G. latifolium Michx. (Biltmore, N. C., the specimens 
kindly furnished by Mr. C. D. Beadle). 
CEPHALANTHUS OCCIDENTALIS (NAUCLEEAE B. et H.) 
The root.—In small shrubs, too young to produce flowers, the 
primary root persists and is quite large; it is of a brownish color 
and measures about 1.5°™ in thickness at the base. At a depth of 
about 9°™ it commences to branch, dividing into a few slender, very 
long branches. Numerous white lateral roots develop on all sides, 
which are very hairy and branch freely. A lateral root of first order 
shows the following structure. Inside the epidermis is an exodermis 
(fig. 1, ex) of thin-walled, pentagonal cells which covers a stratum 
of several cell-layers, a tissue representing cork (fig. 1, p). The 
cortical parenchyma consists of ten strata of thin-walled cells arranged 
radially and with very wide intercellular spaces, sometimes wide 
enough to be called lacunae. Neither starch, crystals, nor raphides 
were observed in the cortex. The innermost layer of the cortex is 
differentiated as a thin-walled endodermis with the Casparyan spots 
plainly visible. A thin-walled pericambium surrounds the leptome 
and hadrome, the primitive structure of which could not be ascer- 
tained since secondary tissues had already become developed; the 
