. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. TRICHOMES. foot of the hair may differ somewhat in shape, size, and arrange- ment from the other epidermal cells. The}- ma}' form an emi- nence upon which the foot rests, or they may be somewhat sunken so that the body of the hair hardly reaches the general surface of the epidermis; but usually the hair projects for a considerable distance above the border of the depression. Both simple and compound hairs may be variously curved and branched, giving rise to ste
. Physiological botany; I. Outlines of the histology of phænogamous plants. II. Vegetable physiology. Plant physiology; Plant anatomy. TRICHOMES. foot of the hair may differ somewhat in shape, size, and arrange- ment from the other epidermal cells. The}- ma}' form an emi- nence upon which the foot rests, or they may be somewhat sunken so that the body of the hair hardly reaches the general surface of the epidermis; but usually the hair projects for a considerable distance above the border of the depression. Both simple and compound hairs may be variously curved and branched, giving rise to stellate and many other forms. 233. Scales are trichoraes which are mostly compound, and consist of discs borne hy their edges or cen- tres, either with or without a short foot or stalk. If the disc is com- posed of radiating cells, the scale becomes stellate, a form which re- sembles or passes into the stellate and tufted hairs common in Mal- vace£E, etc. Well-marked stellate scales are met with in Oleaceoe and Elaeagnacese. 234. JBristles, pricMes and epidermal spines are firmer or stouter outgrowths. When such outgrowths are trulj' epidermal, the}- come off with the epidermis. Hairs, scales, and prickles differ very greatly as to their per- sistence, some being exceedingly short-lived, as, for instance, the hairs which occur on roots; while others, for instance the prickles on the rose, last for long periods. 235. In certain outgrowths from the edges of leaves or else- where the structure is complicated by the presence of a portion of the underlining framework. This is notabl}- the case in the fringe upon the leaves of Droserace£e. There are all degrees of variation between such trichomatous outgrowths and spinulose teeth, or lobes. 236. The consistence of the cell-wall in trichomes varies widely, from extreme tenuity to the densitj- of a silicifled wall. The more delicate hairs are transparent, so that the contents. Fio. 49. Branching unicellular hairs: a, from Hamulus (the
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