324 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
concentration. With solutions' of the acids varying between 1 : 50,000 
and 1 : 60,000 a favourable influence on growth was exhibited. 
Influence of the Rontgen Rays on Germination.* * * § — From a series 
of observations made by MM. Maldiney and Thouvenin on Convolvulus 
arvensis, Lepidium sativum , and Panicum miliaceum, they conclude that 
the effect of the X-rays is to promote germination. The young plants, 
on first germinating, present the usual pale green colour, from which 
it is inferred that these rays have no influence on the formation of 
chloropihyll. 
Germination of the Mistletoe.! — Herr J. Wiesner confirms the state- 
ment that the seeds of Viscum album require a six months’ period of re- 
pose before germination, which cannot take place in the dark, even when 
other conditions are favourable. The seedlings are ombrophobous, 
while those of tropical species of Viscum are ombrophilous. The seeds 
of tropical species also need no period of repose. Light is not essential 
for the germination of the seeds of Loranthus europseus. The prevalent 
idea that the viscin-mucilage of the seeds of the mistletoe is essential for 
their germination is not founded on fact ; they germinate even better 
when freed from it. 
Transpiration of Halophytes. J — Herr O. Rosenberg points out that 
many plants which grow in moist situations nevertheless present par- 
tially xerophilous characters. Employing Stahl’s cobalt-test § for trans- 
piration in the case of a number of marine plants, he states that the 
number of stomates is by no means always a certain measure of the 
amount of transpiration. Many halophytes have not by any means lost 
the power of closing their stomates. The upper surface of the leaf has 
frequently a distinctly higher intensity of transpiration than the under 
surface, a difference not to be explained by the distribution of the sto- 
mates. In certain cases, therefore, the intensity of transpiration is not 
determined by the number and size of the stomates. 
Movement of the Sap in Plants.|] — Herr A. Mayer discusses the 
reversed current stated by Bohm to occur in sunflowers when decapitated, 
and believes that it is a result of the tearing of the tissues. He states 
that, while the cell-walls in the root are permeable for pure water, or for 
water containing a small amount of mineral salts in solution, they are 
not permeable for colloidal organic substances in solution. 
(3) Irritability. 
New Property of Geotropically Irritated RootsA — HerrF. Czapek 
claims to have discovered a change in the chemical reactions of cells 
when exposed to geotropic irritation. A substance which hag the pro- 
perty of reducing an ammoniacal solution of silver nitrate is always 
present in the cells of the root, especially in those of the periblem. But 
* Comptes Rendus, exxvi. (1898) pp. 548-9. Rev. Gen. de Bot. (Bonnier), xii. 
(1898) pp. 81-6 (2 pis.). 
f Ber. Deutsch. Bot. Gesell., xv. (1'897) pp. 503-16. 
X Ofv. K. vetensk. Akad. Forhandl. Stockholm, 1897, pp. 531-49 (1 fig.) (German). 
§ Cf. this Journal, 1895, p. 130. 
|| Forsch. a. d. Geb. d. Agriculturphysik, xx. See Bot. Centralbl , lxxiii. (1898) 
p. 47. Ber. Deutsch. Bot. Gesell., xv. (1897) pp. 516-20. 
