1897] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 321 
appears in cross sections as a protuberance from the cell. The 
thickened walls shows a laminated structure. The side walls are 
not thickened except at places where the thickening has pro- 
ceeded from without inward, often unequally, so that pore canals 
are formed. These are best seen when the scales are mounted 
in chloral hydrate and viewed from the exterior. The inner 
wall usually remains unthickened. Variations, however, occur 
in the different parts of the bud scale in this and other species 
of Abies. Thus Schumann” found that in the upper part of the 
bud scales of A. pectinata the epidermal cells are thickened on 
all their sides. This I find takes place in A. balsamea also. The 
second, or hypodermal layer of cells, remains thin walled. 
The epidermis on the inner side (morphologically the upper) of 
the exposed scales, together with the second or hypodermal 
layer of cells, is usually thickened equally on all sides. The 
epidermal cells of the inner scales covering the growing point 
are thin walled like the cells of the mesophyll. 
I have not succeeded in finding any stomata on the bud scales 
of A. balsamea. It is quite possible, however, that they occur, 
but if present, they are less frequent than in bud scales of 
A. pectinata, where I have found them, contrary to the statements 
made by Griiss*? and Schumann, who both say that they are 
never found on the bud scales of A. pectinata, even in a rudimen- 
tary condition. 
The mesophyll or parenchymatic portion, homologous to the 
mesophyll of the normal leaf, is composed of from three to six 
layers of parenchyma cells, many of which contain chlorophyll. 
he margins of the outer, as well as of the inner scales, are 
_ fringed with filamentous or hypha-like hairs (fig. 7). Although 
the marginal hairs of the outer scales are exposed to the atmos- 
phere, they still remain thin walled, differing in this respect 
: from the exposed epidermal cells and hairs, which always become 
___ ™ScHuMANn, C. G.: Anatomische Studien iiber die Knospenschuppen von Coni- 
_ feren und dicotylen Holzgewachsen. Bibliotheca Botanica 15:3. 1889. 
oe "3 Gruss, J.: Beitrige zur Biologie der Knospe. Jahrbiicher f. wiss. Bot. 23 : 642- 
ol Mii, p. 2. . 
