322 BOTANICAL GAZETTE [ NOVEMBER 
thickened and cuticularized. Tubeuf* finds the marginal hairs 
only on the inner scales of the buds of A. pectinata. They are 
present, however, and always found on the outer scales, also, not 
only in A. pectinata but in all species of Abies whose buds are in 
their winter condition covered with a layer of resin. The mar- 
ginal hairs of the outer scales are always filled with resin. 
With the drying of the cells of the marginal hairs, which always 
remain thin walled and connected with the mesophyll, through 
which the resin canals run, the resin passes from the resin 
canals and inner cells to the exterior, until the bud is covered 
with a layer of resin sufficiently thick to prevent any further 
transpiration of moisture and exudation of resin. 
The endodermis cannot be distinguished. The central bundle 
with its pericycle is composed only of a number of smaller aggre- 
gated cells in the center of the scale. No differentiation into 
xylem and phloem is present. 
A striking character in the structure of the bud scales of 
A. balsamea is that from two to six resin canals are often present 
in each scale. The greater proportion of the scales have two 
canals, the normal number of their morphological equivalents, 
the leaves, but in cross sections of many scales, especially the 
inner ones, one often finds in every bud some scales which have 
from two to six resin canals (figs. 8and 9). As to the origin 
of the increased number of resin canals, whether they are due 
*sTuBEUF: Haarbildungen der Coniferen. Forst.-naturw. Zeitsch. 1896. Son- 
derabdruck S. 19 u. 21 
*6Since the resin canals do not open to the exterior of the bud scales or any 
other part of the plant, there can be no doubt but that there exists a definite relation 
between the marginal hairs of the bud scales and the exudation of resin oP al 
buds. It is evident that the resin, which begins to exude in the late s ummer and fi . 
as soon as the scales begin to dry up, must diffuse through cell pierre pee 
resin diffuses through cell walls has been demonstrated (compare Griiss, tbid., P- 
ah Mayr, Pop. Sci. Monthly 28: 680; and Harz der Nadelhélzer 8o. 1894)- 
not, however, diffuse through the cuticularized and thick wailed ep dermis is cells 
ets the outer scales. 
In many conifers, ¢. g., Picea nigra and P. excelsa, whose buds oh 
any marginal pce tas 
not resin~ : 
cmictal: the bud scales are coriaceous and destitute of resin canals. margit e Te 
hairs of the outer scales of P. migra are thick wailed and the i inner scales seldom © i a 
| 
| 
| 
