68 The Botanical Gazette. [February, 
thickened so as to constitute a U-endodermis. Inside this is 
a simple pericycle, where some cells show a tangential divis- 
ion; the groups of leptome and hadrome border on this peri- 
cycle, asin other roots. But a root measuring about 72™ 
in diameter shows that these tangential divisions of the peri- 
cycle do not produce any secondary parenchyma. There is, 
however, a secondary parenchyma present, but this is located 
in the bark, representing a secondary bark, of which the pri- 
mary layers rest immediately upon the endodermis. The 
secondary meristem, from which these tissues have origina 
ted, has been formed in the innermost layers of the primary 
bark. When this secondary parenchyma developed in the 
bark, the pericycle commenced to show tangential divisions 
in various places, especially where it consisted of from sevéll 
to eight rows of radially arranged cells. 
This increase of the pericycle causes a pressure from the 
interior to the exterior; thus the endodermis becomes tp 
tured in certain places, and a communication opens betweel 
the central cylinder and the cortical zone. The cells of the 
pericycle come to be, in this way, in contact with the second: 
ary bark. These pericycle cells show, thereupon, a begif 
ning sclerosis of their membranes. ‘ 
The result of this investigation is that although the se 
ondary formations in the root of Dracena have originated 
from the bark, the pericycle may, nevertheless, show a certalf 
activity, so as to produce a pressure from the interior to the 
exterior, by which action the endodermis becomes ruptuteé 
A communication is thus established between the two cot 
ducting systems, the primary and the secondary. | 
THEO. HOLM. 
Vegetable ferments. 
There is hardly any branch of physiology which claims out 
attention more than that including the ferments. Inthe a“ 
