1916] 



IIOFFSTADT— PIPER MET 11 YSTICUM 



"5 



2. Each bundle of both the peripheral and pith rings has a cam- 

 bium. The inner ones do not enlarge greatly. The outer or 

 peripheral bundles lay down a ring of wood often 4-5 mm. in thick- 

 ness. The proportion of xylem to phloem is about 8:1 (fig. 18). 



16 



Figs. 16, 17. — Fig. 16, detail of pericycle of P. methysticum; fig. 17, detail of 

 medullary ray; C, cambium; X820. 



Late in the history of. the stem an interfascicular cambium 

 appears (fig. 15), which cuts off segments on the inside only; very 

 late a few segments may be cut off on the other side (fig. 17). 

 This closes the stem cylinder. The interfascicular cambium 

 appears much later in the nodes and remains active much longer. 



