EPIDERMAL GLANDS. 



18' 



it. As the secretion increases, the cuticle becomes more and more raised up 

 from the underlying cellulose wall (De Bary), The balsamic secretion between the 

 cellulose wall and cuticle in the hair-glands or glandular hairs appears in exactly 

 the same way. It is usually the so-called capitate hairs, i. e. hairs consisting of 

 a pedicle-like support and a roundish or broad shield-shaped capitulum, which 

 show this peculiarity ; and it is practically indifferent whether the whole hair 

 consists of a single cell, or a cell series, or a mass of dssue. The secredon 

 appears, as a rule, first at the apex of the capitulum, or, where none is present, at the 

 apex of the cell series, between the wall 

 and the cuticle; and, as the secretion 

 extends from that point, the thin cuticle 

 becomes gradually raised up in the 

 form of a vesicle, the cavity of which is 

 filled with the secretion. An unusually 

 good example of this process is pre- 

 sented in the glandular hairs of Primula 

 sinensis (Fig. 185). The so-called Lu- 

 pulin also, a pulverulent strongly smell- 

 ing substance which may be shaken 

 from the ripe, cone-like, female inflo- 

 rescences of the Hop, consists of glan- 

 dular hairs, which, as Fig. 186 shows, 

 are short, stalked, cup-shaped plates 

 of tissue, the cuticle of which is 

 raised up by the bulky secretion as a 

 hemispherical vesicle, while the cells 

 themselves die. The so-called Hashish 

 arises similarly, in the long-stalked, many- 

 celled capitate hairs of the female plant 

 of the Indian Hemp. In very many 

 other cases, e. g. in the Patschouli plant 

 {Pogosiefuon patschouli), in the Thyme 

 ( Thyinus vulgaris), in Cishis, Pelargonium 

 etc., and also in the Fern Aspidium, the 

 processes are essentially the same. In 

 other cases again the balsamic secretion 

 appears in multicellular glandular hairs, 

 within the generally radially arranged 



septa of the peltate short-stalked capitulum of the hair itself: the septa sjilit into 

 two lamellae, and the intercellular space thus produced becomes filled with the 

 secretion. Such ' schizogenous glands ' are found on the under surface of the leaves 

 of Rhododendron ferugineum and elsewhere. But schizogenous glands may also arise 

 in the epidermis itself, as in the Papilionaceous ^^\■AXi\.Psoralea hirta (Fig. 187), where, 

 by the division of one epidermis cell, a roundish group of cells is developed which 

 extends deep into the dssue beneath and presents an almost globular aggregate, 

 surrounded by the leaf-parenchyma. The septa of this aggregate stand per^ 



l-IG. 187.— Vertical section of the surface of the leaf \^i PsoraUa. 



ta (Papilionacea:). a an almost mature gland after tlie removal of 



I from between the walls by alcohol ; c commencing form - 



tweeii the cell walls ; * very young gland, before 



secretion. It is seen that the glandular cells are only elongated 



epidermal cells (fJe Hary). 



