EPIDERMIS. 6 1 



diverging branches, which may themselves be repeatedly forked — often, as in Matthiola 

 arborescens, with cymose unequal continuation of the successive forked branches. In 

 the forms that are felt-like to the touch, as Farsetia incana, Matthiola arborescens, 

 Alyssum petrseum, Draba spec, the branches rise obliquely from the epidermis up- 

 wards. In others they are parallel to the epidermis, and lying close to it they spread 

 out like a flat star : stellate hairs, e. g. Capsella bursa pastoris, with 2-4 simple rays, 

 Alyssum petraeum, with 3-4 rays once or twice dichotomised. If the body of the hair 

 divides close above the outer surface of the epidermis into two conical limbs, both of 

 which are directed in one line parallel to the surface, the form is attained of a spindle 

 lying parallel and close to the epidermis ; this at its middle passes over into the foot, 

 which is inserted in the epidermis. Such spindle-hairs, with their longer axis as a rule 

 parallel and close to the part which bears them, are characteristic for Cheiranthus cheiri 

 (Fig. 21, D) and Erysimum canescens; they are also to be found among 3-4 rayed 

 stellate forms in Capsella, Erysimum cheiranthoides, &c. 



Similar forms occur in other families: unicellular, appressed, very regular stellate 

 hairs, with sharply conical, short, undivided rays, e. g. on the leaves of Deutzia scabra, 3-6 

 rayed on the upper, usually 9-10 rayed on the under surface. 



In the MalpighiacesE ' there is a similar series of forms, though these are less various 

 than those in the Cruciferae : simple erect conical hairs, and forked, stellate, and spindle- 

 shaped hairs. The erect branched hairs are simply two-forked, with equal or very 

 unequal branches; many-rayed stellate hairs occur in the genus Thryallis; specially 

 large and remarkable, but otherwise of fundamentally similar form to those of Cheiran- 

 thus, are the unicellular appressed spindle-hairs in this family which are termed by de 

 CandoUe (Organogr. p. 103) Malpighiaceous-hairs. 



Another often-described case of the last-named form are the spindle-hairs (' climbing 

 hairs') of Humulus lupulus, with their ends curved like a hook, and borne on an 

 emergence. Further, Weiss (/. c. p. 528) mentions similar appressed spindle-hairs for 

 ' many species of Galega, Astragalus, Acer, Verbena, and Apocynum.' 



{b) Most conical and filiform hairs are multicellular. In the simplest case they are 

 two-celled, so that one transverse wall separates a foot-cell from one cell of the body ; in 

 other cases they consist of more, and even numerous cells (Fig. 21, A a). As regards the 

 form, the same forms appear again, as in the unicellular hairs. One may even say that 

 the same hair may be uni- or multicellular, i. e. that the formation of transverse walls is 

 of minor importance ; thus the long conical hairs on the leaf of Pelargonium zonale are 

 sometimes unicellular, sometimes they have i or 2 transverse walls ; in the latter case they 

 are somewhat thicker-walled than in the former. Unbranched, multicellular, filiform, 

 and conical hairs are the commonest form of all. Examples: leaf of Cucurbitaceae, 

 Solanum tuberosum, and its allies ; most Labiatae (Stachys, Salvia, Thymus, Plectranthus, 

 and others, but not all genera) ; many Compositae (Helianthus, Cnicus, &c.) ; Trades- 

 cantia spec. ; the huge yellowish-brown hairs, up to 3 cm. in length, on the base of the leaf 

 of several species of Cibotium, which appear in the shops as Pingawar Djambi, Pulu, &c.* 



Among the branched forms, in the first place, those described under the unicellular 

 hairs recur as pluricellular. Hairs of the form of a T, that is, stalked spindle-hairs, with 

 pluricellular stalk and unicellular cross-piece in the Anthemideae (Pyrethrum roseum, 

 Tanacetum Meyerianum Sz., Artemisia absinthium, A. camphorata, according to Weiss, 

 /. c). Stellate hairs with unicellular, often rather irregular star, or even two stars, one 

 above another, on a pluricellular stalk : Hieracium Pilosella and its allies. (Fig. 21, Cb, 

 comp. Weiss, Rauter, /. c.) 



Polypodium lingua has stalked, umbrella-shaped, very regular stellate hairs, in which 

 the foot, the erect stem, the centre, and each ray of the star, are single special cells (Fig. 

 21, E). In the Hymenophylleae ' are found pluricellular forked- and stellate-hairs. As 



' A. de Jussieu, Monographie des Malpighiacees, p. 96, pi. II. 

 " Compare Fliickiger, Pharmakognosie des Pflanzenreichs, p. 142. 

 • ^ Mettenius, Die Hyraenophyllaceen, p. 65. 



