Chap. III.] DOWNWARD GROWTH OF THE ROOT. 
123 
unripe ends of roots, under any circumstances. 
But when part of a woody root is accidentally 
exposed by the wearing away of a bank, &c., 
the layer below the outer cuticle will be found 
green, precisely the same as on a branch; though 
where the root goes under ground, both nearer 
and farther from the stem, the under layer will 
be white. The layer under the outer cuticle 
may also be observed green at the commence¬ 
ment of the root of a young tree, when it is acci¬ 
dentally exposed near the neck of the plant. 
This is not a matter of opinion, but a matter of 
fact, and we have only to use our eyes to see it. 
On the other hand, since writing this, I have 
observed that, in those parts of the stems of 
seedlings which pass through earth, the piths 
and the herbaceous envelopes are as white as 
those of roots. I say those of roots, for I 
have also observed that the tap-roots of seed¬ 
lings have piths of precisely the same size as 
the stems. And I doubt not it will be found 
that the roots, as well as the stems, consist 
Solely of alternate layers of pith and wood, with 
one outer skin or cuticle. If roots have no piths, 
what are the rays or silver grain in the roots of 
oaks? Non-medullary rays? In the experi¬ 
ments which I have detailed, with a view to 
That roots have 
no piths an 
error. 
