126 BOTANICAL GAZETTE [AUGUST 
Van TIEGHEM calls attention to the one-sided action of the cam- 
bium in his work on Piper nigrum. 
Vat 
f 
19 Pues 
Fics. 18, 19.—Fig. 18, section of peripheral ring of the bundles of P. methysticum 
at a mature node, showing banded appearance of the rays, X35; fig. 19, tangential 
section of peripheral bundles, showing branch gap; 7. 
os 
The medullary ray becomes lignified and in longitudinal 
section shows pitted cells. At the node in the largest stems avail- 
