ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 261 



occurs in the Equisetaceae. The bud which is formed in the axil of each 

 tooth of the sheath which incloses the base of each internode, receives its 

 vascular system from the lowest region of each bundle of the internode 

 above it. Each leaf is separated from the stem by a layer of suber. 



Anatomical Structure of Loranthacese. * — Herr G. Marktanner- 

 Turneretscher treats of the physiology and anatomical structure of Viscum 

 album. Specially worthy of notice is the fact that the assimilating tissue, 

 in its specific form as palisade-tissue, is not formed till the second year. 

 The ends of the fibrovascular bundles were examined, and it was found 

 that the tracheides terminated generally in a club-shaped swelling. The 

 fibrovascular bundles in the leaf had no parenchymatous sheath. The 

 stomata were found in all possible stages of development in the mature 

 epidermis. 



The author then describes the anatomical structure of Loranihus euro- 

 pseus. Periderm is found in the stem in an early period, and this constitutes 

 one of the differences between LorantJms and Viscum. The deciduous 

 leaves have no typical palisade-cells, and the fibrovascular bundles have no 

 parenchymatous sheath. Frequently, as in Viscum, the tracheides end in a 

 club-shaped manner. The formation of the water-receptacles is charac- 

 teristic on the margin of the leaf near to the apex. They consist of a 

 spherical aggregate of conical cells, which cells, on account of the constitu- 

 tion of their cell-walls, are known as mucilage-cells. The author points 

 out the relation of these mucilage-cells to the ends of the fibrovascular 

 bundles, and in conclusion states that rhombohedric crystals of calcium 

 oxalate are to be found in the parenchyma of the stem. 



Formation of ThuUae.j — Herr J. F. A. Mellink describes a peculiar 

 structure in the leaf-stalk of NymjyJisea alba, consisting of large cavities 

 opening outwards by a narrow fissure, and reaching from the epidermis to 

 the vascular bundles. The large air-cavities in the neighbourhood of these 

 wounds were filled with hair-like structures resembling thullse in their 

 mode of development, since they result from the swelling of the parenchy- 

 matous cells which bound the intercellular spaces. 



Epidermis as a Reservoir of Water. J — According to M. J. Vesque, it 

 is very rarely that the functions of the epidermis are confined to those of 

 protection. Even when it is reduced to a single layer of cells, it serves, 

 in the great majority of cases, also as a reservoir of water, giving it up to 

 the assimilating tissue when the latter is in need of it. For this purpose it 

 is necessary that the epidermal cells should possess the power of changing 

 their volume, and that their osmotic properties should be less than those of 

 the cells to which they give up their water. The mode is described in the 

 paper by which this property of the epidermis was directly proved in the 

 case of a large number of plants. The mean quantity of water given up in 

 this way to the assimilating tissue is 40 per cent, of their maximum volume. 

 The general absence of chlorophyll from the epidermal cells appears to be 

 an adaptation to promote this function ; water passes with very great ease 

 from one cell of the epidermis to another. 



Aquiferous System in Calopliyllum.§ — M. J. Vesque gives a compara- 

 tive sketch of the arrangement of the aquiferous system in the leaves of 

 certain species of Calojpihyllum, and sees in the variations in the arrange- 

 ment of this system a means of classifying the species of this genus. 

 Between the secondary nervures of the leaf, lying below the palisade-cells, 



* SB. K. Akad. Wiss. Wien, xci. (1886) pp. 430-41 (1 pi.). 



t Bot. Ztg., xliv. (1886) pp. 715-53 (1 pi.). 



i Comptes Reudus, ciii. (1886) pp. 762-5. § Ibid., pp. 1203-5. 



