. A textbook of botany for colleges and universities ... Botany. LEAVES 623. Fig. 915.—A capi- tate, multicellular glandular hair from a geranium leaf {Pelar- gonium)j showing the accumulation of an oil drop (0) just beneath the cuticle (c); highly magnified. with a head and with a more or less evident stalk; the cells, both in the head and in the stalk, vary in number from one to several and are rich in cytoplasm (figs. 914, 915; also fig. 632). In the mints the glandular hairs occur in leaf depressions and are relatively stalkless. In some plants (as in Silene) there is a region of palisade-
. A textbook of botany for colleges and universities ... Botany. LEAVES 623. Fig. 915.—A capi- tate, multicellular glandular hair from a geranium leaf {Pelar- gonium)j showing the accumulation of an oil drop (0) just beneath the cuticle (c); highly magnified. with a head and with a more or less evident stalk; the cells, both in the head and in the stalk, vary in number from one to several and are rich in cytoplasm (figs. 914, 915; also fig. 632). In the mints the glandular hairs occur in leaf depressions and are relatively stalkless. In some plants (as in Silene) there is a region of palisade-like secretory cells instead of glandular hairs, while in many plants ordinary epidermal cells ex- crete wax, varnish, etc., as previously noted (p. 570). In oil glands the secretions gather within the walls of the head cells, where they press the cuticle away from the other layers of the wall, ultimately bursting it and discharging to the exterior. The cuticle may or may not regen- erate, but in any event old glands lose the power of excretion, the oil ac- ^. cumulating in the cell lumen. Many water plants (as Brasenia and Nymphaea, fig. 916; also fig- 80s) possess slime glands, which secrete copiously. In the gold- back and silverback ferns (Gymnogramme) there is a glandular waxy secre- tion copious enough to give the leaves their char- acteristic color. - Many plants possess in- FiG. 914. — Hairs from a vervain leaf (Verbena stricta); con- trast the pointed, thick- walled, unicellular ''protective" hair (p) with the capitate, thin- walled, multicellular glandular hair (&), the latter being much the richer in protoplasm both in the stalk and in the head (/z); •«, nucleus; highly mag- 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 Coulter, John Merle, 1851-1928; Barnes, Charles
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