. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. CENTRIC LEAVES 165 tective hairs can be gauged by comparing the rates of evaporation of water from three similar wide-moutlied bottles (about 8 oz. capacity), the neck of one being protected by a cardboard collar about IJ inches high, and that of a second by a similar collar filled with thistle-down or cotton-wool. Each bottle should be filled originally with the same volume of water, and this should again be measured at the end of the experiment. After a few days' exposure in the open air, preferably when it
. An introduction to the structure and reproduction of plants. Plant anatomy; Plants. CENTRIC LEAVES 165 tective hairs can be gauged by comparing the rates of evaporation of water from three similar wide-moutlied bottles (about 8 oz. capacity), the neck of one being protected by a cardboard collar about IJ inches high, and that of a second by a similar collar filled with thistle-down or cotton-wool. Each bottle should be filled originally with the same volume of water, and this should again be measured at the end of the experiment. After a few days' exposure in the open air, preferably when it is windy, it will be found that the bottle with thistle- down has lost least water, whilst that unprotected by a collar has lost most. There are, however, many other peculiarities that are asso- ciated with plants exhibit- ing a struc- ture that tends to reduce transpiration. A feature which often accompanies a reduction of leaf-surface is the absence of markedly dorsiventral structure. In its extreme form this results in the leaf acquiring radial organisation, it becomes centric, and it may then closely resemble a stem. Such is the leaf of the Jointed Rush [Juncus articnlatus), whose sheathing base passes over into an almost cylindrical lamina with a slight concavity on the upper side which faces the stem. The transverse section (Fig. 86) presents an epidermis with thick outer walls and a pronounced cuticle. The sunken stomata [St.) are distributed at intervals. Fig. 86.—Transverse section ol the leaf of the Jointed Rush (Jiincus articnlatus). The upper figure shows a diagram of about half the section, the lower a small segment on a larger scale. C, assimilatory tissue ; p., parenchyma ; , central cavity ; St., stoma ; , vascular 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 work.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectpl, booksubjectplants
