BOTANY. h 
Stomata occur on all portions of the plant, especially in the green parts. 
They rarely exist in the Cellulares or in pale parasites, and never in roots and 
etiolated plants. ‘The number varies greatly in different portions of the same 
plant, being, however, greatest on the under side of leaves exposed to the air, 
and yet sometimes entirely wanting on the upper surfaces. In floating leaves 
the stomata only occur on the upper surface. ‘The following table ex- 
hibits the number of stomata to the square inch on the leaves of several 
plants : 
Plants. Upper Side. | Under Side. Plants. | Upper Side. | Under Side. | 
Mistletoe . . .| 200 200 | Yueca . ./| 40,000 | 40,000 | 
Tradescantia . . 2000 2000 | Mezereon . none 4000 | 
Rheum palmatum| 1000 | 40,000 | Peony . .| none 13,000 | 
Crinum amabile .| 20,000 | 20,000 | Vine. . .| none 13,600 
Aloe . . . .| 25,000 | 20,000 | Lilac. . .| none | 160,000 | 
Clove Pink . .| 38,500 | 38,500 | Holly . .| none 63,000 | 
| 
Various processes are seen at times on the surface of the epidermis by the 
outward enlargement or projection of some cells. When these are more con- 
siderably elongated they constitute hairs ( pili or villi), and are covered by the 
cuticle as by asheath. They are either lymphatic or glandular, the latter 
distended at the base or apex, to receive certain secretions. In respect to 
position, hairs are erect or oblique, or else he flat along the surface (ad- 
pressed); when attached by their middle, they are peltate. They may be 
composed of a single cell, which is either simple, forked, or branched ; or else 
of several cells, which are either placed end to end, as in moniliform hairs, or 
united laterally into a compound cone, compound hairs, or branched. When 
several hairs proceed from a common centre, they are said to be stellate or 
radiated. ‘These, when close pressed together, so as to form a discoid ex- 
pansion, constitute a scale or scurf (lepis); the surface is then said to be 
lepidote. This character is well seen in Hippophae. A chaffy substance, 
surrounding the base of the leaves of ferns, consisting of elongated flattened 
cells, is constituted by ramenta or ramentaceous hairs: a similar substance 
in palms is called reticulum or mattula. Prickles (acwlei) are hardened 
hairs, connected solely with the epidermis. These differ from thorns, 
which are stunted branches, and are connected with the wood. WSef@e are 
bristles or stiff hairs; the surfaces on which they occur are said to be sefose 
or setaceous. 
Hairs, in regard to their form, are clavate, or club-shaped, when they 
expand gradually from the base to the apex, or are thickened at the apex ; 
when there is a distinet rounded head, they are capitate ; when they have 
slight projections on the surface, they are scabrous ; hooked or uncinate, 
when with a hook at the apex turned downwards; barbed or glochidiate, with 
two or more hooks around the apex; peltate, when attached solely in the 
middle ; ciliate, when surrounding the margin of leaves. 
Hairs are found on various parts of plants, even in the interior, and 
7 
