THE VEGETABLE CELL. 5 



(fig 8) are, as a rule, distinguished from the short parenchymatous 

 ceils, not only by their elongated, often fibrous shape, but also by 

 the two ends being attenuated to points. In this case they are not 

 arranged end to end in lines, but their attenuated extremities are 

 interposed between the lateral surfaces of the cells situated above 

 and below them; while the parenchyma cells, if, as is usual, they 

 are arranged in lines, stand one upon another with flattened ends, 

 their cavities being thus separated by partitions directed at right 

 angles to their longitudinal axes. Link founded upon this differ- 

 ence of the ends the distinction between parenchymatous and pro- 

 senchymatous cells, a distinction which is indeed well grounded 

 when we compare extreme forms, but which is by no means to be 

 carried through, since the most manifold transitions occur from 

 parenchymatous cells, with more or less oblique cross-walls, to 

 perfect prosenchymatous cells. 



In many Thallophytes, especially in many^Fungi (e. g., Boletus 

 iijniarms) and Lichens (e, g., in Evernia), isolated portions of 

 the substance are found of fibre-shaped, frequently irregularly 

 interwoven cells (IrregalaT cellular tissue of Kieser). Gradual 

 transitions also occur from tliis form of cell to the form of the 

 parenchymatous cell. 



The form of the parenchymatous cells is most intimately con- 

 nected with theii' relative position. 



The simplest condition is afforded by such cells as lie one above 

 another in a simple row, as the cells of the Oonfervce (pi. 1, fig. 1), 

 articulated hairs, &;c. Here the cells become flattened on the sur- 

 faces of contact, while the side-walls retain their natural curvature. 

 Accordingly as these possess a cylindrical curvature, or one more 

 approximating to a globe, does the entii^e cellular filament obtain 

 a cylindrical or beaded shape. 



When parenchymatous cells lie side by side in a p. ^ 

 simple layer, as is the case in the leaves of most Mosses 

 and JungeomiannlcB^ and in the epidermis of the higher 

 plants, their lateral surfaces, by which they are cohe- 

 rent together, become flattened; while the lower and 

 upper free sides are either more or less convex, coni- 

 cally elongated (fio*. i), or quite flattened like the rest Ceiisofthe 



rn 1 ^ 111 n i n 'x j.1 j? i* epidennis of the 



Taken as a whole, such cells exhibit tlie lorm ol many- petal of 

 angled plates or prisms, the shapes of which again pre- "^^'^'j^''^.^^*'" 

 bent modifications, accordingly as the growth of the 

 cells in the direction of the surface, which they combine to form, 

 is uniform or irregular. The lateral faces of tabular cells are 

 usually perfectly flat. Yet it sometimes happens, for instance in 

 the anthers of Ghara^ and in the epidermal cells of many leaves 

 (fig. 5), that the side-walls are curved into waving lines, or jzig- 

 jgaggecl in sharp angles. 



It is not so easy to define the form of the parenchymatous cells 

 when they are collected together in masses (fig. 6)^ as is the rule 



