178 BOTANICAI. GAZETTE [MARCH 
epidermis are undulate on both faces, and many very large secretory 
cells occur on the dorsal, besides stomata; the latter have mostly 
one pair of subsidiary cells parallel with the stoma; unicellular hairs, 
often with apex hooked, abound on the dorsal face. In transverse 
sections the epidermis appears to be slightly thickened on both faces, 
and the lumen of the cells is somewhat wider on the upper than on 
the lower, excepting the secretory cells, which, as stated above, are 
very large. The stomata are raised, and in the leaves the air cham- 
ber seems constantly to be wide but shallow. 
A chlorenchyma is represented by one layer of palisades on the 
upper face and by three or four strata of very open pneumatic tissue 
on the lower. Three thick-walled layers of collenchyma are located 
on the leptome side of the midrib, inside the epidermis; no stereome 
was observed. A water-storage tissue of thin-walled, colorless cells 
in about five layers in a very broad group cover the leptome, making 
the midrib very prominent on the dorsal face. Neither the collen- 
chyma nor the water-storage tissue was observed at the other nerves. 
Cells containing raphides were only found in the chlorenchyma, 
between the palisades and the pneumatic tissue. All the nerves are 
surrounded by parenchyma sheaths of small, rectangular cells with 
the Casparyan spots very plainly visible, having more the aspect of 
an endodermis than of the usual parenchyma sheath in leaves. The 
midrib is the thickest on account of the very broad collateral mestome 
strand, and because accompanied by collenchyma and water-storage 
tissue. The lateral veins are very thin, and orbicular in cross-section; 
they are collateral and the parenchyma sheath is very distinct as in 
the midvein. 
The characteristics of G. pilosum are the leaf epidermis with 
resiniferous cells and their cuticular striations. Secretory cells in 
epidermis are recorded by SOLEREDER (p. 505) from Rubia, Antho- 
spermum, and Nenax, but not from Galium. They are mentioned 
however, by KEarnev, who found them in the leaves of G. hispidulum 
Michx.*® The collenchyma is well represented in the stem, but is 
confined to the midrib in the leaves. The coloring matter observed in 
the root is well known in other species of Galium, as well as in Rubia. 
_ ¥6 Report on a botanical survey of the Dismal Swamp region. Contrib. U. 5. 
Nat. Herb. 5:506. 1901. 
