66 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Crossing of Cultivated Plants.* * * § — Herr W. Rimpau has experi- 
mented on the crossing of some of our most common agricultural plants. 
If a new form exhibits great variability in its descendants, it is pro- 
bably a hybrid ; while if its descendants maintain great constancy, it 
may be regarded as a spontaneous variety. Of wheat the author de- 
scribes ten artificial and nine natural hybrids; he obtained a fertile 
hybrid between wheat and rye. Of barley, two artificial and six natural 
hybrids are described ; in no case could a two-rowed form be fertilized by 
the pollen of barley with a larger number of rows. Of oats five natural, 
but no artificial hybrids were obtained. Peas produce very few natural 
hybrids; with the beet crossing is much easier. 
Pollination of the Primrose. f — Dr. R. Cobelli gives some measure- 
ments of the length of the corolla-tube and other points in the long- and 
short-styled forms of the primrose. He believes that, whether cross- 
fertilized or self-fertilized, pollination cannot take place without the 
agency of insects, and that these are chiefly TJirips and small Coleoptera ; 
Goniopteris Rhamni is also efficacious in effecting cross-pollination. 
(2) Nutrition and G-rowth (including- Germination, and Movements 
of Fluids). 
Effect of the Electric Light on Vegetation.} — M. G. Bonnier has 
made experiments on the effect of the electric light on the growth of a 
number of herbaceous plants, the illumination being kept up continu- 
ously for a period of seven months. He finds that, under glass, the 
electric light greatly accelerates the growth of herbaceous plants, pro- 
ducing an intense green. The structure of the organs is at first strongly 
differentiated ; but if the light is intense and prolonged for months, the 
new organs formed in the plant present remarkable modifications of 
structure in their various tissues, and are less differentiated, but always 
rich in chlorophyll. The direct electric light is, by its ultra-violet rays, 
injurious to the normal development of tissue, even where the lamps are 
at a distance of more than three metres. 
When trees ( Pinus austriaca , P. sylvestris , beech, oak, birch) are ex- 
posed to a strong electric light, without interruption, by day and night, 
the plant appears to become exhausted by the continuous respiration, 
and the development of the tissues is feebler. Intervals of bright electric 
light and of darkness produce a similar effect, though not so marked. 
Influence of Position on the Form of Organs.§ — Prof. J. Wiesner 
distinguishes between anisotropy, or a change in the direction of growth 
due to external forces, and anisomorphy, or a change in the form of an 
organ caused by its position in relation to the horizon, or to its mother- 
axis. One of the most common illustrations of anisomorphic organs is 
anisophyllous leaves. With regard to the direction of growth, organs 
may be either orthotropous (vertical), hemiorthotropous, or clinotropous. 
The author further defines the following kinds of unequal growth : 
epitrophy , when the growth of the cortex or wood is greater on the upper 
* ‘ Kreuzungsproducte landwirthschaftlicher Cultur - pflanzen,’ Berlin, 1891, 
14 pis. See Bot. Centralbl., li. (1892) p. 359. 
f SB. K. K. Zool.-Bot. Gesell. Wien, xlii. (1892) pp. 73-8. 
% Comptes Kendus, cxv. (1892) pp. 447-50, 475-8. 
§ SB. K. Akad. Wiss. Wien, ci. (1892) pp. 657-705. 
