596 BRITTON: VEGETATION OF THE 
with curious branched hairs, These hairs also occur on the upper 
surface, though not as abundantly. These hairs are nearly stel- 
late, or radiating, but are not very closely appressed and must be 
of great value in preventing the loss of water. Between the 
branched hairs on both surfaces are small glandular hairs. The 
branched hairs (see p/. 26, 2) are very similar to those of Czstus 
Creticus L.. and the glandular hairs resemble those of Czs¢us ladan- 
iferus L., both of which are figured by Solereder.* The palisade 
layer makes up half the thickness of the leaf and the mesophyl 
tissue is rather compact. Each bundle contains spiral vessels and 
has a sheath of parenchyma-cells. 
Versascum Tuapsus. — Both upper and under surfaces of the 
leaf are covered with peculiar branched multicellular hairs, which 
must be an important factor in preventing loss of moisture through 
transpiration. Glandular hairs which are also multicellular occur 
on both surfaces. The branched hairs are long, having a central 
axis the length of which is from twice to three times as great as 
the thickness of the leaf. The central axis is pointed at the apex 
and bears one, two or three whorls of pointed, horizontal, lateral 
branches. 
Linarta CANADENSIS. — Leaf narrow with revolute margins. 
The upper epidermis is composed of colorless cells which are ex- 
tremely irregular in size and shape. Irregular papillae or wart-like 
projections on the surface of the leaf result from the irregularity of 
the cells. The lower epidermis is quite similar to the upper epi- 
dermis except under the midrib, where the cells are much larger 
and more regular in shape. The entire epidermal tissue is adapted 
for holding water. Stomata occur on both surfaces of the leaf, and 
are not depressed, but sometimes occur on the raised portion. 
Curysopsis FALCATA. — Leaf conduplicate on drying. Epider- 
mal cells of both surfaces nearly uniform in size and shape and 
with outer walls very strongly thickened. There are two palisade 
layers — one beneath the epidermis on each surface. Between the 
two palisade layers is a row of small mestome bundles surrounded 
by parenchymatous tissue, made up of large thin-walled mostly 
colorless cells. Some of these cells form sheaths for the bundles, 
and others occupy the space between the sheaths. Green color- 
* Solereder, H. Systematische Anatomie der Dicotyledonen, 92, /- 2/- 1898. 
