THE SEEDLING AND YOUNG PLANT a 
If, in addition to these successive transverse sections, 
we examine a carefully prepared longitudinal section, 
cut so as to pass accurately 
through the median plane of 
the root, the comparison not 
only establishes the above con- 
clusion, but it enables us to be 
certain of yet other facts (fig. 6). 
Such a section shows the root- 
cap covering the tip as a thimble 
the end of the finger, and the 
rim of this root-cap is evidently 
fraying away behind; the cells 
of which it is composed die 
and slough off as the root 
pushes its way between the 
abrading particles of soil. Ob- 
viously this loss of worn-out 
tissue must be made good in 
some way, and closer exami- 
nation shows how this occurs. 
The extreme tip of the root 
proper fits closely into the cap, 
and evidently adds cells to the 
inside of the latter, and thus 
replaces the old ones which are 
worn away. At this true tip 
ph 
Le 
rc. 
Fig. 6 —Diagrammatic sec- 
tion throughthe end of the 
root of the oak. ec, root- 
cortex ; é, piliferous layer; 
7c, root-cap; m, the true 
embryonic tissue (so- 
called ‘ growing-point ’ ) ; 
ph, phloém ; 2, xylem. 
of the root, moreover, we make another discovery— 
namely, that all the cells are there alike in shape, size, 
