560 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
nutates 90°. From sunset until about 10 p.m., tbe plant regains its 
vertical position, and the leaves droop so that their apices point vertically 
downward. From 10 p.m. to 1 a.m. is the period of repose. From 1 a.m. 
till sunrise there is a gradual turning eastward, accompanied by a rising 
of the leaves, their upper surfaces being brought again at right-angles to 
the light. 
The period of repose cannot be entirely due to the fall of temperature ; 
since, although there is a rapid fall from sunset till midnight, there is 
also a rapid fall from midnight to sunrise, when the change of position 
is very marked. The drooping of the leaves cannot be explained 
entirely as a means of protection against excessive radiation ; for when 
the temperature is lowest, the leaves are already standing up rigidly and 
turning towards the east. 
A moderate wind or cloudy weather has but little effect on nutation ; 
continual drought and excessive moisture both act prejudicially. De- 
capitation and wounding do not interfere with the nutation, while, on the 
other hand, the removal of the leaves entirely destroys the power. 
Helianthus rigidus exhibits similar phenomena, but more strongly 
developed. 
Tendrils of Entada scandens.* — Prof. D. T. Macdougal describes 
the structure and irritability of the leaf-tendrils of this plant belonging 
to the Mimoseac. They appear to be equally sensitive over their entire 
length, and are in a state of rapid circumnutation, and more or less 
curved into a hook form. The sensory zone consists of the single layer 
of epidermal cells, in which the nucleus occupies a central position. 
The curvature of the tendril is due to the contraction of the cells that 
become concave, resembling that of the pulvinus of Mimosa. The 
author concludes, from the phenomena presented by this plant, that the 
efficiency of the tendril is by no means dependent on the degree of 
dorsiventrality exhibited, those of Entada being isodiametric. 
Influence of Low Temperatures on the Direction of Shoots.f — Herr 
K. Vochting had previously established that, in the case of flower-stalks 
(Anemone stellata) 1 high temperatures cause an elongation of curved 
stalks and an erect growth ; low temperatures, on the other hand, a curv- 
ing of straight stalks. He now shows that in herbaceous plants this law 
operates, probably very generally, in vegetative shoots also. They be- 
come orthotropous or plagiotropous according to the temperature. The 
species on which the experiments were chiefly made was Mimulus Tilingii. 
Although this law probably accounts for the prostrate direction of the 
stems of many plants, especially of arctic shrubs, it cannot be regarded 
as the only cause ; there are also heliotropic and geotropic factors. 
Contraction-Movements of Anther-lobes, Sporanges, and Moss- 
leaves.:!: — From a series of experiments on the bursting of anthers (7w- 
lipa, Crocus , Lilium , Gladiolus ), and of sporanges (Equisetum arvense ), 
and on the rolling up of dried moss-leaves (Bhynchostegium murale ), 
Herr C. Steinbrinck supports the view of Kamerling that the pheno- 
* Bull. Torrey Bot. Club, xxv. (1898) pp. 65-72 (1 fig.). 
t Ber. Deutsch. Bot. Gesell., xvi. (1898) pp. 37-52 (1 fig.). Cf. this Journal, 1894, 
p. 227. % Ber. Deutsch. Bot. Gesell., xvi. (1898) pp. 97-103. 
