648 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and tlie generative layer retains longer its power of division. A general 
sclerosis wliicli hinders the development of the plant, must be dis- 
tinguished from a local sclerosis which increases the differentiation of 
the tissues and is an indication of a higher organisation. 
Potassium and sodium salts have opposite effects on the tissues ; the 
former retarding the differentiation of the supporting elements, whilst 
the latter increase the rigidity of the plant. Potassium silicate gives a 
dark green colour to the leaves. Potassium phosphate is altogether in- 
dispensable to the plant. 
A very large number of results are given with respect to the influence 
of different mineral salts, in different degrees of concentration, on a 
variety of cultivated plants, both in aqueous solutions and in the open 
ground. The first effects of a salt on the development of a plant are 
often in opposition to the final result, the exuberance of growth being 
due, at least in part, to an accumulation of water. 
Conducting-path of Organic Substances.*— From a variety of ex- 
periments made on living plants, Herr F. Czapek draws the following 
general conclusions. 
The conducting-bundles run down from the lamina of the leaf sepa- 
rately through the petiole without anastomosing ; the conducting-path 
of the carbohydrates cannot therefore lie through the fundamental 
parenchyme ; the current can take place only through the leptome- 
bundles of the leaf-stalk, and in a nearly straight direction without any 
transverse branches ; the conducting elements are exclusively the sieve- 
tubes and the cambiform cells, especially the latter. In addition to 
starch, sugars are of common occurrence in the sieve-tubes. The 
leptome-parenchyme is the storehouse of the leptome ; starch is stored 
up in its cells in great quantities, also often a large amount of reserve- 
proteids. Dead portions of the leptome have no power of conveying the 
products of assimilation. The process is intimately connected with the 
functions of living protoplasm, which takes up the nutritive substances 
and gives them out again from cell to cell. The protoplasmic connec- 
tions of the sieve-tubes play, therefore, a very important part in the 
conduction of food-materials. The individualising of the separate 
members of a stock is a reaction induced by the cessation of the inter- 
change of food-material between the stock and the cell that is thus 
separated. 
Function of Leaves.! — From the fact (which he has confirmed by 
direct observation) that the amount of nitrogenous substance, and 
especially that of asparagin, decreases during the night, M. U. Suzuki 
concludes that one important function of leaves is the splitting up of 
proteinaceous substances into amido-bodies ; these amido-bodies being 
then conveyed to the fruits, roots, underground stems, &c., where they 
are required for the formation of proteids. 
Passage of Food-material into and from the Leaves.! — Herr E. 
Eamann confirms the statement of Wehmer that (contrary to the usual 
* SB. k. Akad. Wiss. Wien, cvi. (1897) l te Abth., pp. 117-70. 
f Bull. Imp. Univ. Tokio, iii. (1897) p. 241. See Bot. Centralbl., lxxv. (1898) 
p. 18. 
X Zeitschr. f. Forst. u. Jagdwesen, xxx. (1898) pp. 157-66. See Bot. Ztg., lvi. 
(1898) 2 fe Abth., p. 231. 
