334 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Development of the Gesneriacese.* — According to Dr. K. Fritsch, the 
tubers of Sinningia and Gorytholoma originate from a hypocotyledonary 
tubercle ; while the scaly subterranean stolons of Achimenes and Kohleria 
are found on the first year’s plant, as axillary shoots of the cotyledons 
and of the first pair of foliage-leaves, 
New Myrmecophilous Plant. f — Prof. 0. Penzig describes an Abys- 
sinian shrub, Stereospermum dentatum , belonging to the Bignoniaceae, in 
which there is a peculiar contrivance for the housing of ants. The 
insects are attracted by extra-floral nectaries on the under side of the 
leaves, and they form themselves a home in the following way. A 
false dichotomy is produced by the destruction of an axillary bud. 
The internode between the branching is then hollowed out by the 
removal of the pith, and an aperture to the formicarium is provided by 
an opening in the woody cone which still remains in the place of the 
original axillary bud. 
j 3. Physiology. 
(2) Nutrition and Growth (including Germination, and Movements 
of Fluids). 
Amount of Light which is favourable to the Growth of Plant s.J — 
Prof. J. Wiesner has studied the amount of light which is effective in 
promoting the growth of plants, and has come to the following conclu- 
sions : — Plants (like Lemna) which receive an unlimited amount of light 
do not produce a maximum of organic substances. In by far the greater 
number of plants the amount of light absorbed is diminished by the form 
and position of the organs. In trees this amount is reduced, in the 
peripheral portion of the foliage to J or J, in the central portion to 
-gL- of the possible amount of light. All luxuriant vegetation is pro- 
duced under conditions of comparatively feeble, and especially of diffused 
daylight. Intense light is of no advantage to a plant growing in 
unfavourable conditions, especially in poor dry soil. Although the actual 
amount of light enjoyed by trees and shrubs is greater in tropical than 
in temperate regions, yet in the latter the leaves of deciduous woody 
plants receive a more intense light than those of the former at one 
particular period of the year, viz. at the commencement of the period of 
vegetation. 
Action of Light on the Form of Plants.§ — Prof. K. Goebel gives 
the result of a series of observations on the effects of light in modifying 
the external form of plants, especially in the case of the Cactaceas. The 
general result of an increase of light was greatly to increase the super- 
ficial area of the organs. 
Effect of Climatic Conditions on the Growth of Trees. II — M. E. 
Mer states that the effect of the very dry season of 1893 in the Yosges 
was detrimental to the growth of the trunks of the trees in girth, and 
still more to the length of the shoots. The low temperature and 
great moisture of the air during the summer of 1888 had a similar 
* Ber. Deutsch. Bot. Geselh, xii. (1891) Gen.-Vers.-Heft, pp. 96-102. 
f Malpighia, viii. (1895) pp. 466-71 (2 pis.). 
% Ber. Deutsch. Bot. Geselh, xii. (1894) Gen.-Yers.-Heft, pp. 78-89. Cf. this 
Journal, 1894, p. 475. § Flora, lxxx. (1895) pp. 96-116 (5 figs.). 
j| Comptes Rendus, cxx. (1895) pp. 275-8. 
