i824 A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 1726. — Canuirea ericoides. Malpighiaceae. Flower in 

 longitudinal section. {After Baillou.) 



of the genus Dicella. This phloem appears to arise from the cambium 

 which for a time may cut off phloem elements internally, thereafter re- 

 verting to xylem formation. In many of the lianas grooves appear in the 

 xylem which are themselves lined with cambium and in some genera 

 there are furrows in the stem corresponding to these xylem grooves 

 (Fig. 1727). The most elaborate condition is seen in the stems of 

 StigmatophxJIon in which the xylem at first grows in thickness by the 



Fig. 1727. — Tetrapteris. Malpighiaceae. 

 Trans\erse section of an old stem showing 

 the dissected xylem masses. {After 

 Schenck.) 



activity of a normal cambium and is surrounded by a rather wide circular 

 phloem. The xylem contains abundant xylem parenchyma and broad 

 medullary rays with the result that the xylem appears to be broken up 



