1907] HOLM—RUBIACEAE 167 
the upper face and along the margins, also along the veins on the 
lower face; moreover the lateral walls of the epidermis are straight, 
not undulate, on the upper face and do not show local thickenings. 
Cells with raphides are frequent in the pneumatic tissue, and a col- 
lenchymatic tissue occurs on the leptome side of the midrib. All the 
mestome bundles are collateral, and the median is the largest. Gland- 
ular hairs like those described and figured for H. coerulea were 
observed along the margins of the stipules. 
The characteristics of this species are the local thickenings of the 
lateral cell walls of the epidermis of the leaves, and the presence of 
collenchyma, which seems to be absent in H. coerulea. 
MITCHELLA REPENS (ANTHOSPERMEAE B. et H.) 
In systematic works Mitchella is generally called an herb; “a 
Smooth and trailing small evergreen herb” in the 6th edition of 
Gray’s Manual, or “‘a small creeping evergreen” in Gray’s Synopti- 
cal Flora. By Nutratt it was considered as “an herbaceous repent 
evergreen;” BrNnTHAM and Hooker describe it as “herba repens,” 
with no allusion to the leaves being evergreen; while Linnaea in this 
same work (Gen. Plant.) is characterized as “‘fruticulus repens, sem- 
pervirens.” Finally Schumann (Natiirl. Pflanzenjam.) describes 
Mitchella as “kriechende Krauter” (M. repens and M. undulata); 
while in this same work Linnaea borealis is called “niederliegende 
Stréuchlein.” Linnaea and Mitchella are both evergreen and both 
possess creeping, woody stems. MITCHELL, who was the first to 
describe our plant, called it Chamaedaphne, which shows that he 
had the correct impression of the plant as being an “undershrub” 
and not an “herb.” Moreover, a plant cannot at the same time be 
an herb and an evergreen, and Mitchella is an undershrub in exactly 
the same sense as is Linnaea. 
The stems are creeping, and the roots develop usually near the 
nodes and often two together, or commonly they develop from one 
to three at some distance from the nodes, and mostly from the lower 
face of the internode; the color of the roots is yellowish or light brown. 
All the internodes are stretched, and the opposite leaves have distinct 
petioles and green blades, the outline of which may vary from ovate 
to almost orbicular; no scale-like leaves develop in any place on the 
