160 GLANDS. [BOOK i. 



they have been well distinguished by Link. According to 

 that botanist, they are either simple (fig. 16. a, b, d, g, h, i,) 

 or compound (c, f } k, I, m ) ; the former consisting of a single 

 cell, and placed upon a hair acting as a simple conduit, 

 occasionally interrupted by divisions ; the latter consisting of 

 several cells, and seated upon a stalk containing one or more 

 conduits, formed by rows of cellular tissue. They are com- 

 mon upon the rose and the bramble, in which they become 

 very rigid, and assume the nature of aculei. For the sake of 

 distinguishing them from the latter, they have been called 

 setae by Woods and myself, but improperly ; they are also the 

 aiguillons of the French. In Hypericum they abound on the 

 calyx and corolla of some species, but do not give out any 

 exudation; they contain, however, a deep red juice within 

 their cells. In some Jatrophas they are much branched; 

 in many Rueworts (Rutaceae) they form a curious humid 

 appendage at the apex of the stamens. 



The glandular apparatus of plants has received the atten- 

 tion of Meyen, who has published on the subject an elaborate 

 paper, from which the foregoing figures are taken. He 

 admits the distinction of simple and compound glands, and 

 regards them both as unquestionable organs of secretion. 

 To some of the former he assigns occasionally more cells than 

 one in the gland that terminates them; but the hair to 

 which they belong is always simple. He gives the following 

 account of the well-known glands that clothe the leaves of 

 the Sundew, and which have a very complicated structure; 

 the hair exhibits in its interior a spiral tube which penetrates 

 deep into the apex of the gland, but there is no trace of a 

 cavity in the gland. The hairs which form the stalk of the 

 gland are not simple excrescences of the upper walls of the 

 epidermal cells, but true excrescences of the substance of the 

 leaf, and appear so much more early, that the whole hair and 

 its head may be said to be covered by the epidermis. In 

 young organs of this kind, Meyen proceeds to say, it may be 

 seen distinctly that the gland-head is nothing more than the 

 apex of the compound hair which at a later period thickens. 

 Afterwards the stalk (that is, the hair) extends to a great 

 length, and thus the cells all acquire a lengthened form. 



