TRANSACTIONS OF THE SECTIONS. 99 
of the principle in trees that chiefly conduces to the development of the same— 
namely, that of the root. When I thus distinctively allude to the “ Root Principle,” 
I hold that in all cases of the vegetable structure there are invariably two distinct 
and separate processes going forward in the development of each separate tree or 
plant—the one from the root upwards, which I, on a former occasion before the 
British Association, some years ago, in Liverpool, denominated, in contrast with the 
above, “the Leaf Principle,”’—these being as it were the two extreme ends or 
turning-points in the circle of assimilation, and continually more or less in action, 
according to the stimuli arising from light, air, heat, and moisture,—the leaf being 
so far analogous to the lung in animals, and the spongiole or root to that of the 
heart,—the one, from the combined action of atmosphere, light and heat, conducing 
to the deposition of woody fibre, or the annual layer of wood in the tree, and the 
ramification of that wood into numerous roots and rootlets; the other, from the 
action of soil and its various constituents, to the development of buds, leaves, flowers, 
and fruit,—this beautiful and simple process of circulation passing separately up and 
down without intermixture, but evidently, I conceive, by distinct sets of vessels, 
through the alburnous layer between the bark and the wood, externally in Dicotyle- 
dons, and internally as it relates to Monocotyledons. Nor do I consider that we can 
ever actually change the course of these principles so as to invert their results. Cut 
the tree by a mortise section, as shown by the figure in Lindley’s ‘ Theory of Horti- 
culture,’ p. 36, or rather look at the figure on p. 35, and you will see an exact 
representation of the embryo development of the leaf and root principles alluded to; 
as they became developed in the course of my experiments quoted. In short, the 
leaf cannot long exist without the root, nor the root without the leaf ;—the one and 
the other are evidently equally essential to vegetable life. I stop not, however, to 
dwell upon the multitudinous variations and modifications of the two principles in 
- question to be met with amongst the various genera and species of plants (as, for 
instance, the Cacti and other succulents), as what I above describe may be sufficient 
for my present purpose. To the point,then. In the management of fruit-bearing 
trees, whilst much doubtless will depend upon the nature and quality of soil, situa- 
tion, aspect, &c., as it regards the growing process, much more as to fruit bearing 
will depend upon the manipulation, position, form and nature of the roots. I doubt 
not the growing specimens presented will readily illustrate this,—the roots being com- 
pletely washed clear of the soil, so as to facilitate examination. In these two fruit- . 
bearing dwarf trees with the numerous roots, I present specimens planted only sia 
months since ; in the other two specimens you have the same varieties ; but on another 
form of roots, barren, and likely so to be for three or four years to come., It may 
: now be said, how is all this? I will shortly endeavour to tell you. In the fruit- 
bearing Pear, the stock worked upon is the Quince, a close congener of the genus 
Pyrus, namely, Cydonia vulgaris, remarkable for the minute subdivision and conse- 
quent number of its rootlets, forming, as may be observed, a perfect wig. The other, 
but barren tree, is of the same kind and date of grafting, but worked upon the 
common Pear stock—or Pear grown from the seed pip—in other words, the Crab 
Pear, the roots of which are few, deep, and straggling. In the case of the fruit- 
bearing apple, the stock worked upon is what is called the Paradise; that is, the cut- 
ting from a certain kind of grafted apple that is highly productive of roots and root- 
lets, as in the case of the Quince above noticed. The other, but barren Apple, is also 
of the same kind and date as that just mentioned, but worked on the common or Crab 
stock, raised in like manner from the seed or pip, and, with the barren Pear, nearly 
equally deficient in fibres. The cause of this remarkable contrast of precocity on the 
one hand, and barrenness on the other, arises chiefly from the forms and positions of 
their roots. In those with fruit, the numerous spongioles or feeders of these twiggy 
rootlets at once answer the question as to precocity, as tending, from the immediate 
action of air, heat and moisture, to the rapid maturation of the ripening process and 
consequent development of flower-buds., On the other hand, as it regards the barren 
specimens presented, you at once see how different are the forms and distribution of 
the roots: in these they are more in the form of tap-roots running deep into the soil 
and subsoil, and away from the more direct influence of solar heat and air, thus 
_ lessening greatly the ripening process in the wood so conducive to flower-bud forma- 
tion, and thereby otherwise going to the production of strong tohg-jointed water- 
; i* 
