EPIDERMIS. 



93 



of Thymus (Fig. 39), Lophanthus, Satureja: also the longer stalked scales of Lavandula 

 multifida, &c. (comp. Martinet, /. l., Taf. 11). The celebrated glands of the Hop (Fig. 

 40, Rauter, Martinet, /. c.) are multicellular peltate scales, 

 depressed In a cup-like or conical manner, and covered 

 when mature by the bladder-hke gland, which is usually 

 raised conically, and therefore the whole appears as 

 though it consisted of two cones with their bases in con- 

 tact. As found by Meyen, the yellow glands on the foliage 

 of Ribes nigrum closely resemble them in structure, but 

 are always flatly disc-shaped. 



On the extended glandular surfaces, as that of the epider- 

 mis of the branch of Betula, I have no further details to 

 adduce. Of the sticky zones of the Sileneae, it may be still 

 more definitely stated that the rather difficult determina- 

 tion whether the secretion is formed from the peculiar 

 prominent epidermal cells alone (Unger), or from the 

 epidermis of the whole sticky zone, requires further investigation. 



Among the circumscribed spots, which are usually called simply ' glands,' or compound 

 (external) glands, two things may be distinguished from one another. First, closely 



Fig. 38. — Pogostemon Patschouli ; 

 young leaf, transverse section, Piece of 

 epidermis, witli a short glandular liair ; 

 secretion dissolved by alcohol (375). 



Fig. 39.~Epidenni5, with glandular scales, of the upper side of the leaf of Thymus vulgaris {375). a surface view. 

 b transverse section ; secretion removed by alcohol. 



circumscribed groups of glandular, capitate hairs, which are closely 

 congregated. These constitute the round, pale or dark violet- 

 red spot on the under surface of each stipule of certain vetches 

 (Vicia Faba, sativa, sepium^), which consists in Vicia Faba of 

 closely congregated, club-shaped, capitate hairs, of equal height, 

 with short foot or pedicel-cell, and a head consisting of two 

 pairs of cells one above another : glandular properties have not 

 been observed in it in this species. The cells of the head con- 

 tain strongly refractive bodies, forming dense globular aggre- 

 gations or granules, together with colourless or violet cell-sap. 

 In Vicia sativa a sugary fluid is excreted, in a manner as yet 

 not exactly observed ". Further the ' glands ' on the under side 

 of the leaf of Urena sinuata are club-shaped, closely crowded, 

 capitate hairs, which Une a deeply-hollowed depression. Again, 

 the so-called glands on the under surface of the leaf of Catalpa 

 syringaefolia and C. Bungei' consist of groups of top- or fan- 

 shaped scales with unicellular stalks, similar to the scales 

 of Hippuris. These, as regards their structure, obviously do not 



Fig. 40. — Humulus lupuius ; 

 glandular scales, transverse sec- 

 tion (142). A before the secretion 

 begins, the thick cuticle firmly at- 

 tached to tlie surface of the cells. 

 — B cuticle raised high up by the 

 secretion, which h-as begun; se- 

 cretion removed by alcohol. 



belong to this category, 



C. C. Sprengel, Entd. Geheimniss, p. 356. ' Compare Fuckel, Flora, 1846, p. 417. 



' Caspary, De Nectariis, p. 40. 



