Development, and Structure of the Vegetable Cell. 2^1 



growing with them in the juice of the cell, and either nucleated 

 or non-nucleated according to the chemical constitution of the 

 plasma, or are enclosed between these during their growth, and 

 absorbed ; at any rate, they disappear. 



The two newly formed and very thin-walled cells subdivide 

 within the cavity of the mother cell, and so completely occupy 

 it, and are so intimately moulded to its walls, its pores, rings, 

 and spiral windings that they can scarcely be distinguished 

 from its membranes. In the same way, the septum, which owes 

 its origin to the apposition of the two daughter cells within the 

 parent cell, is of such great tenuity as to appear like a single 

 lamella. 



The same new formation proceeds in the cells of the cortical 

 tissue next the epidermic layer; and in this region the newly 

 formed tissue extends from the cut surface almost as deeply 

 within the cell-tissue as the dead portion of the vascular bundles. 

 These newly formed pairs of cells are always arranged, in the 

 upper section exposed to the air, in a direction perpendicular to 

 the adjoining dry and air-containing cell-tissue, and more or less 

 indeed in the same peculiar manner as the cork- cells of the bark, 

 forming uninterrupted rows with the successively produced 

 young cells. These are united in the parenchyma in a plane pa- 

 rallel with the cut surface, and which, close to the epidermis and 

 round the vascular bundles, is turned inwards. By this means 

 the surfaces of the dead extremities of the vascular bundles pro- 

 jecting into the living parenchyma are invested by a sheath 

 formed by a stratum of cell-series standing perpendicularly to 

 their longitudinal axis. 



This production of cork-cells is moreover found not only in 

 the cells of the parenchyma, but also in the cells and vessels of 

 the vascular bundles; so that even the latter become occupied by 

 a layer of cork-cells, and the undisturbed tissue of the internode 

 is separated by this intimately adherent layer of cork-cells from 

 the withered tissue, and also protected from the immediate in- 

 fluence of the atmospheric air. 



The cork-cells do not always arise in pairs, but in larger 

 number sometimes in cells of greater length. In the elongatecJ 

 cells of bast and wood, as well as in the vessels, there are usually 

 numerous cells, arranged in rows, beginning at the end to- 

 wards the cut surface, filling up the long cells more or less 

 completely. In the vessels, moreover, they still oftener give 

 origin to an irregular tissue. 



The enlargement of the cells filled with transparent fluid, 

 produced together with the cell-nucleus, must take place with 

 extraordinary rapidity in the vicinity of the cut surface, in the 

 manner that may be directly observed in the tissue-cells of a 



