g6 CELLULAR TISSUE. 



but to others treated of above. From these must be distinguished the glandular epi- 

 dermal spots, which protrude, but not in the form of hairs. A number of these have 

 it is true the characteristic bladder-like, glandular structure of the wall, as for example 

 the round glandular spots on the under side of the leaf, especially in the angles between 

 the three main ribs of Clerodendron fragrans, Vent., and others, but not all species 

 of the genus ' ; the round spots, 2-3 of which are to be found on each side of the 

 mid-rib at the base of the under surface of the leaf of Prunus Laurocerasus ^ ; the more 

 or less depressed cup-like glands forming the end of the conical, stalks or teeth on the 

 base of the petiole of the Passifloras' (observed on P. atrocserulea, Hort.); the pairs of 

 round glandular spots, which protrude at the upper end of the petiole in species of 

 Stigmatophyllum, a genus of the Malpighiacese (S. cristatum, ciliatum) ; and the gland, 

 the structure of which varies according to species, which lies at the upper margin of the 

 basal part of the petiole or phyllode in the species of Acacia. The structure and form 

 of these glandular spots have been given above for Clerodendron and Prunus. In 

 Acacia marginata, R. Br., Calamifolia, Lindl. lophantha, they appear as convex, callus- 

 like prominences, with a depression or furrow on the apex: their epidermis has a 

 glandular structure above the depression or furrow, over the rest of the surface it 

 is firm and tough-walled. In many other species (A. longifolia, latifolia, melanoxylon, 

 subulata, longissima, obtusa, myrtifolia, striata *) the glandular spot lies at the base of a 

 narrow, deep, pocket-like depression with swollen margin. In Acacia pulchella' the 

 glandular hair lies on the end of a cylindrical stalk, which stands half-way between the 

 insertions of the two main pinnae. As already intimated, the cuticle in all these glands is 

 raised up from the membrane by the secretion : in the flat, glandular spots of the Acacias, 

 Clerodendron, and Laurocerasus, it is raised as a wide bladder, which often bursts in later 

 stages of development, and in that case is often not to be found in prepared sections. 

 The very tough cuticle of the stronger glandular spots of Clerodendron usually bursts 

 transversely over the whole surface, with a gaping slit, which is almost visible with the 

 naked eye. The bladder-like, glandular structure of leaf-teeth is to be found, e. g. in 

 Mercurialis annua, Prunus, Salix, and many others "- 



Of the other numerous ' glands ' which occur on leaves and leafy parts, and which were 

 in part named above, including the numerous glandular teeth of the lamina, the peculiarly 

 formed glandular teeth of the petiole and leaves of Viburnum opulus, V. Tinus ', of 

 Ricinus, and species of Cassia, and the numerous glands of the leaves of most 

 Malpighiaceae, Sec, the structure of the surface and the secretion are not yet 

 thoroughly investigated : but all that is known of them coincides so closely with 

 examples which certainly belong to this category, that it is better, at least for the 

 present, to put them in connection with these. 



Intramural glands have not hitherto been described with reference to their characteristic 

 peculiarity of structure, excepting in the above-quoted account of Hanstein. The flat, 

 top-shaped scales of the Rhododendrons, which belong to this category (Fig. 41), are 

 fitted into a depression of the dermal surface, and attached to short 4-5 seriate stalks. 

 Their free outer surface is roundish and flat. They consist, according to the individuals, 

 of 60-80 elongated cells, which form a layer, and diverge radially from the stalk. The 

 ends of all these are directly connected with the stalk, with one another, and with the 

 cuticle at the outer surface. 40-50 of the cells, in a ring-like series, border on the lateral 

 periphery of the scale, and are also in immediate connection with one another, and 



^ F. Fischer, M^m. Soc. des Naturalistes de Moscou, I. p. 246, according to Treviranus, Physiol. 

 II. p- 35 ; Caspary, /. c. ; von Schlechtendal, Botan. Zeitg. 1844, p. 6. 

 ^ Caspary, /. c. 



' Compare Martinet, I.e. p. 191, figs. 238, 239. 

 * Unger, Flora, 1844, p. 703 ; Anat. und Physiol, p. 362. 

 ■ ? De.Candolle, Prodromus, II. p. 455. 

 « Compare Keinke, /. c. ' Unger, Caspary, /. c. 



