ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
659 
phenomenon of luminosity, dependent on respiration. When growth is 
simply the result of swelling, the resulting increase in size can be only 
limited ; active growth must be the result also of intussusception or the 
intercalation of particles of a solid substance. Neither imbibition nor 
capillarity nor air-pressure is sufficient to account for the raising of 
water to any considerable height in the vascular bundles ; it can only 
be explained by the action of forces which are constantly acting afresh 
at distinct points in the path of conduction of the water. 
Germination of the Cocoa-nut.* — M. L. Trabut describes the mode 
of germination of the seed of Cocos nucifera, which agrees in essential 
points with that of palms. When the embryo begins to germinate the 
cotyledon directs itself towards the cavity in the albumen, where it 
grows to an enormous size, and entirely fills it up, consuming the whole 
of the milky fluid which it previously contained. The whole of the 
endosperm is then also absorbed, commencing from within outwards. 
Relationship between Specific Size and Organization.! — Prof. J. 
Sachs discusses the questions of the limits of variation in size in any 
one species of plant, independently of variations in the supply of 
nutriment, and the correlation between the average size and the degree 
of complexity of the organizations. He lays it down as a general law 
that homologous organs of the same or of different species consist of 
cells of nearly uniform size, even when the organs themselves are of 
very different dimensions ; that there is no proportion between the size 
of an organ and that of the cells of which it is composed, the relative 
size of homologous organs being dependent on the number, and not on 
the size, of the cells. 
Nutrition of Insectivorous Plants.J — According to M. N. Tischutkin, 
in the secretion of insectivorous plants — Drosera rotundifolia and longi- 
folia , Dionsea muscipula, Pinguicula vulgaris , and N&penthes Mastersi — 
the process of digestion is entirely dependent on the presence of bacteria 
in the secretion, the part performed by the plant being only the fur- 
nishing of a substratum in which the micro-organisms can live. 
Increase in Girth of Stems.§ — From observations made on trees 
in the Botanic Garden at Edinburgh, Mr. D. Christison states that in 
favourable years the growth in girth extends over six months, from 
April to September, though usually the growing period is considerably 
shorter than this, both with Conifers and with Exogens. The months of 
greatest growth are almost invariably June and July, but with the tulip- 
tree August. The period of greatest development of the foliage does 
not always correspond with that of the greatest development of stem. 
Growth of the Leaf-stalk of Nymph8eaceae.|| — Prof. G. Arcangeli 
has determined that, in several species of Nymphaeaceee— Nuphar lutea , 
Euryale ferox — the leaf-stalks of the leaves which are still entirely sub- 
merged grow faster than those of the floating leaves. This he attributes 
* Bull. Soc. Bot. France, xxxix. (1892) Sess. Extraord., pp. xxxvi.-vii. (1 
t Flora, lxxvii. (1893) pp. 49-81. 
j Acta Horti Petropolitani, xii. pp. 1-19. See Bot. Gazette, xviii. (1893) p. 105. 
§ Trans. Bot. Sci. Edinburgh, xix. (1892) pp. 101-20, 261-333. See But. 
Centralbl., 1893, Beih., p. 196. 
II Bull. Soc. Bot. Ital., 1893, pp. 191-4. Cf. this Journal, 1890, p. 630. 
1893. 2 Z 
