1914] 



BAILEY 6* SINNOTT—PHYLOGENY OF ANGIOSPERMS 



53 



Quercus alba. — The reduction of wide multiseriate rays has 

 progressed much farther in this oak of the subgenus Lepidobalanus 

 than it has in most species of the subgenus Erythrobalanus, for even 

 m vigorous, well nourished shoots and roots vestiges of wide rays 

 persist, in the first formed secondary xylem, only in the vicinity 

 of traces of the leaves and rootlets (fig. 6). The 



withdraw 



from the mature shoots is accom 



evidences 



disintegration, but in the cotyledonary region and 



multiseriate 



mia 



and 



tended by longer trails of disintegrating ray parench 



tissue devoid of vessels. With decreasing vieror. the multiseriate 



* 1G 2 - — Transverse section of a sup- 



Fig. 3. — Transverse section of a vigor- 



pressed, forty-year-old branch of a mature ous, eleven-year-old shoot taken from the 

 specimen of Quercus alba, showing the same tree as the suppressed branch illus- 



retarded development of wide rays. 



trated in fig. 2. 



rays appear at progressively later stages in the development of 

 the stem and root (text figs. 2 and 3), but may be recalled by stimu- 



1m 



Q 



multiseriate 



In this evergreen or live oak the reduc- 

 i has been carried farther than in either 

 The wide ravs are commonlv absent in 



of the preceding species. The wide rays are 

 young stems, but may be well developed in the vicinity of the vascu- 

 lar elements which pass out to the rootlets (fig. 17)- When the 

 wide rays appear during subsequent growth, they are much dis- 

 integrated and may persist in this dissected condition for many 



they may finally become homo- 



tendencv for larze multiseriate 



cases 



years, although in some 

 geneous ray parenchyma. This 



