70 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
either did not germinate at all, or their germination was greatly re- 
tarded ; while, on the other hand, of the alkaloids contained in the 
poppy, narootine, codeine, and narceine stimulated the germination of its 
seeds, morphine and thebaine appeared to produce no effect, and 
papaverine retarded the process. 
Absorption of Water by Leaves.* — Herr A. Burgenstein has made 
a series of observations on the absorption of water by the surface of 
leaves, and comes to the conclusion that, although it may take place to 
a certain extent, through the epidermal cells, the stomates, and the 
hairs, it is of no physiological importance, at least as regards the flora 
of Europe. An exception is furnished by rootless epiphytes, and certain 
xerophilous plants. 
Direct Assimilation of Nitrogen.f — Herren B. Frank and B. Otto 
give a practical application to their previously recorded conclusion that 
the leaves of leguminous plants contain a larger proportion of asparagin 
in the morning than in the evening, owing to their taking up directly 
the nitrogen of the atmosphere. They recommend that those crops 
which are cut green for fodder, such as clover, should be cut shortly 
after sunset. They also point out that, for the same reason, evening is 
the best time for the pasturing of cattle, especially when the weather is 
clear and warm in the day-time. 
Evolution of Oxygen by Plants at low temperatures.} — Accord- 
ing to experiments made by M. H. Jumelle on certain conifers and 
lichens, the suppression of assimilation at temperatures below zero C. 
depends rather on the stoppage of the supply of water than on the low 
temperature itself. At temperatures reduced as low as — 33° and — 35°, 
it was found that branches of Picea excelsa and Juniperus communis con- 
tinued to disengage oxygen in diffused sunlight. The same was the case 
with Evernia Prunastri at temperatures between — 30° and — 20° ; 
while with Physcia ciliaris and Cladonia rangiferina — lichens in which 
the process of assimilation is much less intense at ordinary temperatures 
—no decomposition of carbon dioxide could be detected at very low 
temperatures, even in sunshine. It appears, therefore, that with plants 
which are capable, when moist, of resisting intense cold, the decomposi- 
tion of carbon dioxide may continue at very low temperatures, long after 
respiration has ceased, 
(3) Irritability. 
Sensitiveness of Antherozoids.§ — Herr C. Voegler has investigated 
the sensitiveness of the antherozoids of ferns to malic acid and its com- 
pounds. The observations included all families of ferns except the 
Hymenophyllaceae, Gleicheniaceae, and Marattiaceae. 
The structure of the antherozoids was found to be the same in all 
families of ferns in all essential points, the only variations being in the 
number of the coils and in the length and breadth of the spiral band. 
* JB. Leop. Comm.-, Real.- u. Obergymu. Wien, 1891, 47 pp. See Bot. Cen- 
tralbl., xlviii. (1891) p. 186. 
t Deutsche Landwirths. Presse, xviii. (1891). See Bot. Centralbl., 1891, Beih. 
p. 340. Cf. this Journal, 1891, p. 370. 
7 Comptes Rendus, cxii. (1891) pp. 1462-5. Cf. this Journal, 1891, p. 634. 
§ Bot. Ztg., xlix. (1891) pp. 641-9, 657-63, 673-80, 689-98, 712-7. 
