382 
VEGETABLE PHYSIOLOGY. 
by its being the only one of the elementary organs that is uniformly 
present in plants, and by its being the chief constituent of all those 
compound organs that are most essential to the preservation of the 
species. 
“ It transmits jiuids in all directions. In most cellular plants no 
other tissue exists, and there a circulation of sap takes place; it con¬ 
stitutes the whole of the medullary rays, conveying the elaborate juices 
from the bark towards the centre of the stem. All the parenchyma, in 
which the sap is diffused upon entering the leaf, and to which it is 
exposed to evaporation, light, and atmospheric action, consists of 
cellular tissue ; nearly all the bark, in which the descending current 
of the sap takes place, is also composed of it; and in indigenous plants, 
where no bark exists, there appears to be no other route that the 
descending sap can take than through the cellular substance, in which 
the vascular system is embedded;—it is, therefore, readily permeable 
to fluid, although it has no visible pores. 
“ In all cases of wounds, or even of the development of new parts, 
cellular tissue is Jirst generated. For example: the granulations that 
form at the extremity of a cutting when embedded in earth, or on the 
lips of incisions in the wood or bark ; the extremities of young shoots; 
scales, which are generally the commencement of leaves; pith, which 
is the first part created when the stem shoots up; nascent stamens and 
pistilla; ovula ; and, finally, many rudimentary parts : all these are 
at first, or constantly, formed of cellular tissue alone. 
“It may be considered the jlesh of vegetable bodies; the matter 
which surrounds and keeps in their place all the ramifications or 
divisions of the vascular system is cellular tissue. In this the plates 
of wood of exogenous plants, the veins of leaves, and, indeed, the 
whole of the central system of all of them, are either embedded or 
enclosed. 
“ The action of impregnation appears to take place exclusively 
through its agency. Pollen is only cellular tissue in a particular state ; 
when it bursts the vivifying particles, it contains a still more minute 
state of the same tissue; the coats of the anther are composed entirely 
of it; and the tissue of the stigma, through which impregnation is 
conveyed to the ovula, is merely a modification of the cellular. The 
ovula themselves, with their sacs, at the time they receive the vivifying 
influence, are a semi-transparent congeries of cellules. 
“ It is, finally, the tissue in which alone amylaceous or saccharine 
secretions are deposited. These occur chiefly in tubers, as in the potato 
and arrow-root; in rhizomata, as in the ginger; in soft stems, such as 
those of the sago, palm, and sugar-cane; in albumen, as that of corn ; 
