ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
77 
on the young leaves of Myriophjllum , and finds it to be probably of 
the nature of a glucoside. The chemical reactions arc given in detail ; 
they do not agree with those of tannin. Like tannin-vacuoles, these 
“ glucoside-vacuoles ” are protoplasmic secreting organs, and have much 
in common with elaioplasts. 
Colouring Matters of Underground Organs.* * * § — From observations 
made on several roots and tubers, M. E. Gain asserts that the formation 
of colouring matters in underground organs is not due to the direct 
influence of light, but depends on the accumulation in them of reserve 
food-materials. This accumulation is in general promoted by the dryness 
of the soil. 
Excretions of Calcium Phosphate, j — Herr A. Zimmermann finds 
spherites of calcium phosphate in the living epidermal cells of the stem 
and leaves of a species of Cyperus, and in the fundamental parenchyme 
of older stems. They vary considerably in form — nearly round, irregular, 
or clustered — and consist of a nucleus of calcium oxalate, which is often 
crystalline, of a matrix of calcium phosphate, and of a delicate organic 
envelope. 
(3) Structure of Tissues. 
Relationship between Leaf-development and the Formation of 
Vessels.^; — Herr L. Jost has investigated this subject in the case of a 
number of herbaceous and woody plants. The most marked results 
were obtained with Phaseolus multijlorus, where there is an abundant 
supply of reserve food-materials in the cotyledons. The leaf-traces 
of the first leaves are here completely distinct in the epicotyl, at least 
in the .young plant, and some of them run from the leaf as far as the 
node of the cotyledons without anastomosing, and belong therefore 
entirely to the leaf. The results are on the whole not conclusive, but 
they show that the formation of tissues, and especially the development 
of the xylem, and its dependence on external and internal factors, is a 
very complicated process. 
Stoppages of Vessels. §— Dr. A. Wieler has investigated the causes 
and the results of stoppages of vessels in the case of a large number 
of dicotyledonous and monocotyledonous plants. They may be caused 
either by living tissues (thyllae), by gum, by resinous substances, or by 
excretions of calcium carbonate; while in many cases their nature is 
still unknown. They may occur in all kinds of vessels — annular, 
spiral, and pitted. The depositions of calcium carbonate are apparently 
purely physical ; while in all other cases the stoppage appears to result 
from a vital process in the parenchymatous cells which adjoin the vessel. 
Stoppages occur normally in the vascular bundles, in the duramen and 
alburnum, and in the scars of fallen leaves and twigs. They hinder the 
transport of water into the vessels, and result in the current being 
confined, in the wood, to the last, or the few last, annual rings. They 
also protect the vessels from the injurious influences of atmospheric 
* Bull. Soc. Bot. France, xl. (1893) pp. 95-102. 
f Btitr. z. Morphol. u. Phys d. Pflanzenzelle (Zimmermann) (1893) pp. 311-7 
11 fiO. See Bot. Centralbl., Iv. (1893) p. 272. 
% Bot. Ztg., li. (1893) lte Abtheil., pp. 89-138 (1 pi. and 4 figs.). 
§ Biol. Centralbl., xiii. (1893) pp. 513-24, 577-607. 
