. An introduction to vegetable physiology. Plant physiology. THE AEEATION OP PLANTS 105 cells. Air makes its way into these spaces by a process of diffusion outwards from the cells abutting upon them, and very soon external orifices in the shape of stomata make their appearance. The various constituents of the air make their way into and out of the cell by a process of diffusion, being dissolved in the water of the cell-wall or escaping from such a moist mem- brane according to the conditions existing, and the relation between the internal and external pressure of the particular gas in questio
. An introduction to vegetable physiology. Plant physiology. THE AEEATION OP PLANTS 105 cells. Air makes its way into these spaces by a process of diffusion outwards from the cells abutting upon them, and very soon external orifices in the shape of stomata make their appearance. The various constituents of the air make their way into and out of the cell by a process of diffusion, being dissolved in the water of the cell-wall or escaping from such a moist mem- brane according to the conditions existing, and the relation between the internal and external pressure of the particular gas in question. As soon as the differentiation of fig 71 —cells splitting the tissue in the growing part of .an ^^TaTs™ cT organ begins to take place, the forma- tion of the intercellular spaces can be observed. In these regions they begin by a splitting of the wall between two contiguous cells or at the angles where three cells join (fig. 71). The crevice soon extends and may make its way for a considerable distance round any particular cell. The cavities so come into communication among the cells, each of the latter abutting upon a single one or upon several. While the tissue is young these are very narrow and slit-like, or are only visible at the angles when the cells are polyhedral. They Fig. 72.—Cortex of Eoot, showing Inter- , CELLULAR PASSAGES BETWEEN THE CELLS. rapidly become larger (fig. 72), and in some parts, particularly in the interior of the lower strata of the mesophyll of dorsiventral leaves, they may occupy more space than the cells themselves (fig. 73). Light appears to influence their development somewhat, though no definite relation can be shown to exist between. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Green, J. Reynolds (Joseph Reynolds), 1848-1914. Philadelphia, P. Blakiston
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