712 SUMMARY OF CURRENT RESEARCHES RELATING TO 
exuded from the cut trunk in the rainy season when the air was saturated 
with moisture. He found it amounted to the enormous quantity of 
0* * * § 711, 0*587, and 0*360 litres per hour respectively at three different 
periods of the twenty-four hours, viz. night, morning, and afternoon. 
C3) Irritability. 
Mechanism of the Flowers of Schizanthus.* ■ — Herr 0. Juel de- 
scribes the process by means of which the stamens of Schizanthus spring 
suddenly forward when the flower is visited by an insect, covering its 
abdomen with pollen. The channel of the corolla, in which the stamens 
lie, is clothed with a layer of glandular hairs, the terminal cells of which 
are imbedded in mucilage. This forms a viscid layer which causes the 
filaments to adhere to the lower lip. But a slight pressure, such as is 
caused by the contact of an insect, releases the filaments from their 
confinement, and tension causes them to spring into an erect position. 
Movements of the Stamens of Berberis.t — M. G. Chauveaud has 
investigated the mechanism of the movements of the stamens of Berheris , 
which he attributes to irritability of the protoplasm, not to the presence 
of an intercellular substance, as suggested by Pfeffer. Within the fibro- 
vascular bundle of the filament is a special tissue composed of about 
two layers of elongated cells, the transverse walls of which are thin, 
while the longitudinal walls are thick, but with numerous thin spots. 
This elastic tissue is covered by a layer which is a continuation of the 
epiderm on the internal and lateral faces of the filament, and consists 
of rounded thin-walled cells. This layer of cells is the active element 
in the movements of the stamens. When in a state of repose the proto- 
plasm in each cell is collected into a thick band attached to its base. 
Under the influence of any mechanical or chemical irritation, this band 
stretches and curves so that its central portion presses against the outer 
wall of the cell, and causes it to curve in such a way that the cell 
becomes shorter and thicker. 
Leaf-movement in Cercis.J — Mr. S. G. Wright has studied the leaf- 
movements in Cercis canadensis. He finds prominent enlargements at 
both the upper and lower end of each petiole ; but the former only 
appears to take part in the movements. This pulvinus is composed of 
parenchyme, collenchyme, bast, and woody tissue. The motile organ 
appears to result from cell-division in the parenchymatous tissue ; under 
the influence of light a daily movement takes place in the lamina to the 
extent of nearly 100°. The rise begins about 3 a. m., and continues 
rapidly till 9 a.m. A slight decline then occurs, after which the lamina 
rises to its full diurnal position about 2 p.m. A rapid fall then takes 
place, the full sleep position being reached about 10 p. m. 
Compass Plants. — Mr. T. Meehan § explains the changes in position 
in the leaves of compass-plants — Silphium laciniatum , Lactuca Scariola , 
Gaura parviflora, Chrysopsis villosa — as the result of a twist caused by 
a somewhat prolonged effort of spiral growth, without any reference to 
heliotropism. 
* Ofv. K. Vetensk. Akad. Forh. Stockholm, li. (1894) pp. 67-72 (2 figs.) (German). 
t Comptes Rendus, cxix. (1894) pp. 103-5. 
I Bot. Gazette, xix. (1894) pp. 215-24 (2 pis. and 1 fig.). 
§ Tom. cit., pp.- 158-9. 
