LIFE-HISTORY OF THE HERB ROBERT 95 
from my shady border, is amply provided with 
well-branched roots: growing as it did in a place 
where the ground rarely got parched even on the 
surface, its numerous and finely divided rootlets 
were just the thing for occu- 
pying the moist interstices 
of the soil and for absorbing 
the water films surrounding 
the small particles of which 
it is composed. 
It is, of course, not the 
rootlets as we see them 
with the naked eye that 
pump water into the plant, 
but the very much finer 
and more delicate root-hairs 
which they bear close to, Fra. 35.—Herb Robert seed- 
although not actually on, ee a eee 
the extreme tip. (Photo.) 
Let us now turn to the 
leaves: they play an indispensable part by taking 
from the air in which they grow free oxygen as well as 
carbon dioxide, which yields further supplies of oxygen 
in addition to carbon, and both these elements are 
among the components of starch and other foodstuffs. 
I need perhaps hardly add that this by no means 
exhausts the activities of green leaves in the all- 
important matters of respiration and nutrition. 
And here I should like to say a little about the 
pores through which the air gains access to the interior 
of the leaf. 
I took some little trouble to estimate how many 
there are on an ordinary leaf; and I found about 
ten upon a pjece of the skin so small that it would 
H 

