CHAP. I. 
ELEMENTARY ORGANS. 
247 
route that the decending sap can take than through the cel- 
lular substance in which the vascular system is imbedded. 
It is, therefore, readily permeable to fluid, although it has no 
visible pores. 
In all cases of wounds, or even of the developement of new 
parts, cellular tissue is first generated: for example, the 
granulations that form at the extremity of a cutting when 
imbedded in earth, or on the lips of incisions in the wood or 
bark ; the extremities of young roots ; scales, which are gene- 
rally the commencement of leaves ; pith, which is the first part 
created when the stem shoots up ; nascent stamens and pistils; 
ovules ; and, finally, many rudimentary parts ; — all these are 
at first, or constantly, formed of cellular tissue alone; 
It is that from which leaf buds are generated. These organs 
always appear from some part of the medullary system ; when 
adventitious, from the ends of the medullary rays if developed 
by stems, or from the parenchyma if appearing upon leaves. 
It may be considered the fiesh of vegetable bodies: the 
matter which surrounds and keeps in their place all the rami- 
fications or divisions of the vascular system is cellular tissue. 
In it the plates of wood of exogenous plants, the fibres of 
endogenous plants, the veins of leaves, and, indeed, the whole 
of the central system of all of them, are either imbedded or 
enclosed. 
The action of fertilization appears to take place exclusively 
through its agency. Pollen is only cellular tissue in a parti- 
cular state; when it bursts, the vivifying particles it contains 
are 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 fertilization is conveyed to 
the ovules, is merely a modification of the cellular. The 
ovules themselves, with their sacs, at the time they receive the 
vivifying influence, are a semitransparent congeries of cellules. 
It is, finally, the tissue in lohich alone amylaceous or sac- 
charine 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 ; in pith, as in the 
Cassava; in the disk of the flower, as in Amygdalus; and, 
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