94 PLANT ORGANS OR PARTS OF PLANTS. 



width of the woody cylinder and the pith; shape, size, 

 arrangement, and amount of the starch grains. An 

 important point to remember is that all of these characters 

 are variable, however. The circumstances bearing upon 

 the variability are: (i) the time when root is gathered, 

 younger specimens having fewer hypoderm cells, the 

 walls of the fibrous cells are thinner, the endodermis is 

 thinner, etc. ; (2) the time of year when collected, the 

 character and the amount of the starch grains varying 

 with the season. The root also varies at different dis- 

 tances from the rhizome; parts nearer the rhizome are 

 uniformly stouter in all of the elements. Great varia- 

 bility of the endodermis is to be accounted for in this 

 manner. The following characters express the average 

 rather than the absolute conditions: 



Microscopical Characteristics of Different Varieties.— 

 In Honduras sarsaparilla under low power the cortical 

 and central parts are seen to be about equal in size. 

 Under high power the hypodermis of one or two layers of 

 cells and some root hairs become visible. Just beneath 

 two or three rows of thickened mechanical cells is the 

 cortex proper, consisting of spherical cells with thickened 

 walls having simple pores ; these cells are closely packed 

 with starch grains. The endodermis consists of a single 

 row of cells, more or less quadrangular, the w^all usually 

 being uniformly thickened or in some parts of the root a 

 little thicker on the inside. 



In Para sarsaparilla the cortical portion is two or 

 three times as wide as the central portion. The outer 

 hypodermis is five to seven layers in thickness, the outer 

 walls of these cells being slightly thicker than the inner 

 walls. The cortical cells are rich in compound starch 

 grains. The endodermis consists of cells somewhat 

 radially elongated, which cells are thicker on the sides and 

 inner walls, and conspicuously pored. The pith is white 

 and broader than the vessel portion. Starch is copious. 



