ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
821 
(3) Nutrition and Growth (including- Germination, and Movements 
of Fluids). 
Relation between secondary Increase in Thickness and the Nu- 
trition of Trees.* — Dr. A. Wieler treats in detail of these subjects, 
especially in relation to the diminution of the number of the vessels in 
the autumn wood, the conditions of elongation of the elementary 
organs of the wood, the increase in thickness of the cell-walls in the 
autumn wood, and its relation to the conditions of elongation. Three 
factors play their part in the nutrition of the tree, viz. the conduction 
of water, the supply of inorganic, and the supply of organic food- 
materials. 
Autumn and Spring Flowering Plants. f — Mr. A. F. Foerste gives 
further details respecting the autumn-flowering plants of the South of 
Europe. In many cases the phenomenon is not the result of a second 
blossoming, but of an excessive tendency to blossom early. In a number 
of species the flower-buds blossoming in the autumn are protected in scaly 
bulbs or in subterranean buds until immediately before the flowering 
season. In many cases the blossoms are developed more or less before 
the leaves. Very frequently the fruit is not mature till the following 
spring, the fruiting ovary remaining beneath the ground through the 
winter, as in Colchicum. When there are a number of spring-flowering 
species in the same genus, one or more will always be found to com- 
mence flowering remarkably early, thus forming a link with the autumn- 
flowering species. 
Passage of Substances out of Leaves in the Autumn.f — Herr C. 
Wehmer contests the current statement that before the fall of leaves 
in the autumn there is a retreat of the nutrient substances con- 
tained in them to the branches. The error appears to have resulted 
from a wrong interpretation of the fact that the proportion of potash 
and phosphoric acid in the ash undergoes a great decrease in the autumn 
months. This however is largely due to the enormous increase of other 
substances, that of lime being to the extent of 1400, and of silica as 
much as 5000 per cent. The absolute decrease of potash and phos- 
phates is very much less, and does not take place to any great extent 
before October, when the leaves are already dead, and a transfer 
of substances from cell to cell is impossible. It is largely due to 
solution by rain. The substances contained in the leaves are, it is 
true, used up again by the plant, but only after they have reached the 
soil, and there undergone the necessary transformations. 
Radial Current of Sap in the Roots. § — Dr. P. Siedler has investi- 
gated the structure of the root of a very large number of Phanerogams 
and Vascular Cryptogams, with the view of determining the course of 
the radial current of sap. He finds that there is in many cases a special 
tissue, sharply differentiated from the rest of the cortical parenchyme, 
which especially regulates the centripetal current. This tissue consists 
* Tharander forstl. Jahrb., xlii. (1892) 154 pp. and 2 pis. See Bot. Ztg., 1. (1892) 
p. 511. Cf. this Journal, 1887, p. 776. 
t Bot. Gazette, xvii. (1892) pp. 233-45. Cf. this Journal, ante , p. 389. 
J Ber. Deutsch. Bot. Gesell., x. (1892) pp. 152-63. 
§ Beitr. z. Biol. d. Pflanzen (Cohn) v. (1892) pp. 407-42 (1 pi.). 
