CHAP. I. ELEMENTARY ORGANS. 247 



route that the decending sap can take than through the cel- 

 kilar 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 which alone amylaceous or sac- 

 charine secretions are deposited. Tliese 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, 



R 4 



