ae 
1897] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 313 
with a somewhat prominent midrib or keel below. They are 
always twisted at the base, giving them the distichous direction 
peculiar to species of Abies. The leaves on the erect shoots are 
not transversely heliotropic, or twisted at the base, but grow 
in all directions from the shoot. They are shorter and thicker 
than those of the lateral branches, more or less awl shaped, and 
are sharply pointed at the tip. 
The number and arrangement of the stomata seem to vary 
in different localities. Masters® finds that the stomata are chiefly 
on the upper surface of the leaf. McNab? in his description 
gives two or more rows of stomata in the middle line near the 
apex on the upper surface, with two or more rows on each side 
of the midrib on the lower surface. Bastin and Trimble® find 
the greater number on the lower surface. I find that by far the 
greater proportion of the stomata are on the lower surface of the 
leaves of the lateral branches, which have one band of from 3 
to IO rows on the upper surface, and two bands of 8 to I0 rows 
On each side of the midrib on the lower leaf surface. On both 
Surfaces the stomata are found in greater numbers toward the 
apex of the leaf. The more or less terete leaves of the terminal 
shoots have their stomata distributed about equally on all sides. 
Cross sections of the leaves show a well marked cuticle cov- 
ering the lignified epidermal cells, the outer walls of which are 
cuticularized and much thickened. Immediately under the epi- 
dermis lies the hypoderm when present (fig. 7). As to the 
Presence or absence of a hypoderm, McNab® says that it is want- 
ing. Engelmann” found that the leaves have scarcely any hypo- 
derm cells above, and very few on the edges and keel, fewer than 
any other species of Abies. Sometimes no hypodermal cells 
*MasTeRs, M. T.: Anatomy and life-history of the Conifer. Jour. Linn. Soc. 
27: 250. 
aoe New way of determining species of Abies. Robinson, The Garden 
Ir:2 
_ ®Bastrn and TRIMBLE: A contribution to the knowledge of some North Ameri- 
can Conifers, Am. Jour. Pharm. 68: 556. 
° Lbid., p. 280. 
2 *° ENGELMANN, G.: The American firs. Gard. Chron. N, S. g : 300. 78 
