i84 



LECTURE XI. 



cell, which, as it slowly developes, undergoes many divisions in all directions, so that 

 a multicellular mass of tissue of roundish form arises, the cells of which subsequently 

 become remarkable as containing very granular, apparently dead protoplasm. Later 

 on, the thin cell-walls dissolve ; the process commencing in the middle of the 

 spheroidal group and proceeding outwards. There thus arises a roundish cavity, 

 filled partly with watery sap, partly with drops of ethereal oil or balsam — the 

 products of solution of the mass of cells. The layers of tissue surrounding this 

 cavity fit closely on all sides, without intercellular spaces, and thus form a kind of 

 wall to the receptacle for the secretion (well seen in the leaves of Citrus). These 

 processes will be sufficiently understood on comparing figures 183 and 184; the 

 relations there illustrated appear with few deviations to be exactly the same in the 

 internal glands of the Myrtaceae, other Rutaceae, and in Hypericum, Gossypitim (Cotton), 

 Lysimachia and species of Oxalis. 



Very many plants\ particularly among the Dicotyledons, owe the more or less 



Fig. 1S5. — A portion of the epidermis with ijlandular 

 hairs, from the petiole of Primula sinensis, a com- 

 mencement of tlie development of secretion ; b a large 

 bubble of secretion; rf after the bursting of the bubble 

 (De Bary). 



Fig. 186.— Lupulin gland of 

 the Hop. A young, before the 

 secretion separates ; B older, 

 the cuticle raised up by the 

 secretion (De Bary). 



Sticky condition of the surfaces of the leaves and young shoot-axes to epidermal 

 glands, as is easily perceived by passing the fingers over the surface of such plants. 

 As a rule, the secretion at the same time possesses a strong specific odour, as in 

 the glands before mentioned. The glandular condition of the epidermis proceeds in 

 many cases from secretions developed by the epidermis cells themselves, as is very 

 conspicuous under the nodes of the stem of Lychnis viscaria, on the young 

 shoot-axes of the White Birch {Betula alba), on the teeth of the leaf of Prunus and 

 species of Salix, and on small areas on the underside of the leaf of Prunus lauro- 

 cerasus and others. The viscid secretion appears here on the epidermis cells 

 (which are otherwise intact, but sometimes distinguished by being particularly small 

 and peculiar in shape) between the proper cell-wall and the cuticle situated upon 



* Cp. Johannes Hanstein, ' Ueber die Organe der Harz- Jtnd Schleiviabsondentug^ ' Bot. Zeitg.' 

 3, p. 697 ; and also the much better description in De Bary's ' Vergl. Anat' § 19. 



