_212 The Botanical Gazette. [July, 
the collenchyma being most numerous on the tangential walls, 
e markings of fibrovascular elements are of the common 
form in this type of plants. The arrangement of the proto- 
plasmic body of the organ with reference to density and com- 
position, bears a direct relation to the sensitiveness of any 
part of the organ. The protoplasm is most dense and richly 
granular in the epidermis and chlorophyllous cells of the con- 
cave'surface near the tip. The density decreases as it passes 
back into the middle region where it is quite uniform through- 
out. The contents of the epidermal cells and collenchyma of 
this side take the stain most deeply as does the epidermis of 
the convex side, which, as well as the underlying tissue, is 
very similar over the entire surface. : 
t may be assumed in conclusion, that the concentration 
of the protoplasm in the epidermal layer has a direct connec: - 
tion with irritability, that the movements of the organs are 
due to changes in the chlorophyll layer and that the disposi- 
tion of the xylem elements is favorable to rapid flexion and 
extension, and that the abundant supply of reserve food ma- 
terial is a provision for the rapid growth and fixation of the 
tendril upon coiling. 
Purdue University, La Fayette, Ind. 
EXPLANATION OF PLaTE XIV.—Fig. 1. Half cross section of middle portion of 
—Fi e of same.—Fig. 3. Long! 
tu nal section of concave side of same. a, a’ epidermis; 2, 4’, col poss ee 
¢’, chlorophyll parenchyma bast; ¢, xylem; /, pith.— Biber 
of tip dril sh g cavity, a.—Fi avity of same see 
-—fig. 6. Longitudinal section through tip of mature tendril. 
in fig. 1; ¢, F io 7 Di 
toplasm in tip and part of middle region of tendril. 
An apparatus for determining the periodicity of root 
press 
M. B. THOMAS. 
{WITH PLATE XV.) 
received 
nd the results of 
