512 MISS ISABEL MCCLATCHIE ON 
Their structure is normal, but the relatively early differentiation of the 
xylem is rather unusual. The root-cap is a dermacalyptrogen, as in the 
adventitious root itself. In the ruptured cortex there is a fair amount of cork 
formation and also numerous tannin cells. | 
“ Branching” of adventitious roots and production от rootlets. 
The aerial roots sometimes appear to dichotomise (text-fig. 18 с) or to 
develop three or four apices (text-fig. 18 d and e). In transverse section 
а b с 
и р з 
f / \ 
` Ad ) 
SEN 7 " Nu _ 
d e f 
Ета. 19.—a-e. Sections through the apex of the root shown in fig. 18e; 4-7. Serial sections 
through another root showing apparent dichotomy. The dotted areas indicate 
the formation of cork. Ж-о. Sections through a root-apex showing division 
into four, 
the vascular ring appears to become two-, three-, or four-lobed, as the case 
may be, and there is often no sign of injury. Text-fig. 19а, b, and е, show 
three transverse sections of the root figured in text-fig. 18 с. 
According to Němec *, this type of branching in roots is caused by an 
injury to the root-apex, by which the tip is unevenly decapitated and the 
torn plerome has an irregular surface with two or more projections. These 
* Némec, ‘Studien über die Regeneration.’ 
