660 
SOMHARY OF CURRENT RESEARCHES RELATING TO 
to the vertical pressure of the water on the upper surface of the sub- 
merged leaves due to the lower specific gravity of the leaf. 
Transport of Search in the Potato.* * * § — M. A. Girard confirms the 
statement of Prunet that the starch which is originally formed in the 
primitive cells of the tuber of the potato is dissolved as the shoots 
develope, and is transported towards the cells of these shoots, filling 
them up and becoming fixed in the normal form. 
Graft-hybrid.f — Mr. H. L. Jones records an instance of a graft- 
hybrid between two varieties of geranium, a pure white and a pure red 
one. Some of the flowers had two red and three white petals ; in others, 
some or all of the petals were red mottled with white. 
(3) Irritability. 
Irritability of the Tendrils of Passiflora.i — Mr. D. T. McDougal 
thus sums up his observations on the movements of the tendrils of 
Passiflora ccerulea and Pfordti. The tendrils and terminal internodes 
show circumnutation. The tendrils are extremely sensitive to contact 
with solids and with liquids at a temperature of 40° C., but are not 
sensitive to liquids at ordinary and low temperatures, unless they are 
so applied as to induce direct osmotic action, nor to slight electrical 
stimuli. Coiling round an object takes place on contact, while the 
formation of spirals takes place on maturity. The formation of the 
spirals exerts a tension of 3-20 grm., shortening the tendril one-third 
of its length; a mature tendril can withstand a strain of 350-750 grm. 
Contrary to the experience of Darwin with Bryonia and Echinocystis , the 
tendrils of Passijiora are sensitive to contact with one another. 
(4) Chemical Changes (including Respiration and Fermentation). 
Physiology of Leaves.§ — Mr. H. T. Brown and Dr. G. H. Morris 
give a historical resume of researches on the occurrence and formation of 
starch in plants, and then the result of experiments of their own, chiefly 
on Tropseolum and Eelianthus. They believe that starch is not a necessary 
link between the sugars of assimilation and the sugars of translocation, 
a large portion of the assimilated products not passing through this con- 
dition at all. The occurrence of diastase was found to be universal in 
quantity sufficient to transform the whole of the starch present in the 
leaf. It is to the presence of diastase, and not to the action of living 
protoplasm, that the disappearance of starch is due. The only sugars 
found in the leaves of Tropaeolum were cane-sugar, levulose, dextrose, 
and maltose, and of these maltose and dextrose appear to be the sugars 
which contribute most to the respiratory requirements of the leaf-cell. 
It is probably in the form of maltose that most of the starch passes from 
cell to cell. 
Function of Salts of Calcium and Magnesium. || — According to 
Herr C. Wehmer, the relative amount of salts of calcium and magnesium 
* Comptes Rendus, cxvi. (1893) pp. 1148-51. Cf. this Journal, ante, p. 355. 
f Bot. Gazette, xviii. (1893) p. 111. 
% Tom. cit., pp. 123-30. Cf. this Journal, 1892, p. 817. 
§ Journ. Chem. Soc., 1893, pp. 604-77. 
Landwirthsch. Jahrb., 1892, pp. 573-70. See Biol. Centralbl., xiii. (1893) 
p. 257. 
