124 BOTANICAL GAZETTE [AUGUST 
dense cell contents. Late in the history of the plant the pericycle 
becomes lignified. There is no differentiated endodermis in either 
old or young stems. 
In the cortex: of the young stem is a continuous band of tissue 
7-8 cells wide, which responds to the test for suberin (Tun- 
MANN 16). This is in patches in the older stems. The intercel- 
lular spaces of the pith are very large. 
See 
15 
Fics. 13-15.—Fig. 13, young stem of P. methysticum after differentiation has 
been pees X80; fie, 14, one X1ot; fig. 15, sector of stem after interfascicular 
cambium has been developed, X10 
Secondary activity in the stem 
There are two methods by which the stem of Piper methysticum 
enlarges: (1) by active division of pith cells; (2) by cambail 
activity. 
1. In the center of and at irregular intervals throughout the 
pith, groups of cells will divide actively throughout the internode. 
