1897 ] NORMAL AND DISEASED ORGANS OF ABIES BALSAMEA 323 
to the branching of the two canals already present, or whether 
they are peculiar to the scales of A. balsamea, 1am not able to 
state. It appears, however, that in all species of Abies whose 
buds are covered over with resin in the winter, there is an 
increase in the amount of resin production in the bud scales 
over that produced in the normal leaves, and hence it is proba- 
ble that more than the normal number of canals can develop in 
the bud scales. The resin canals are seldom surrounded by a 
layer of strengthening cells. 
The growing point with its rudimentary leaves is covered 
over by the inner scales, which are imbricated, and cover the 
apex of the growing point four to six layers deep. Longitu- 
dinal sections of the growing point show that in its winter con- 
dition no tissue differentiation whatever has taken place. The 
central portion (plerome) has pith characters. In cross sections 
no resin canals or rudimentary bundles are present. 
The septum (Knospenscheide or Scheidewand) , which makes 
the break in the pith at the annual nodes in most species of 
conifers, is well developed in buds of A. dalsamea. It consists 
of from six to ten layers of thick walled cells, forming a dia- 
phragm, separating the pith of the growing point and young 
shoot from the pith of the last year’s internode. Immediately 
below the diaphragm there is always to be found a mass of 
loosely connected, rounded pith cells (fig. 70, f, g), which in 
older internodes have separated from the septum, or diaphragm, 
so that a cavity is formed. This empty chamber is seldom pres- 
ent below the septum of the bud in its winter condition. In the 
‘Spring, however, as soon as the differentiation of the peripheral 
cells of the plerome begins, and the xylem cells of the vascular 
bundle begin to elongate, the septum is partly raised above the 
loose tissue of the pith of the last year’s internode, thus forming 
the pith chamber, which is always present below the septa of the 
first and second year old and older internodes. 
Fritsch’? found that the cells of the septum are in the form 
_. "7FRitscu, Cari: Die Markliicken der Coniferen. Schriften d. Kgl. physik. 
Okonom. Gesellschaft zu Kénigsberg 25 : 50. 1885. [Separat-Abdruck p- 6] 
