650 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
chlorophyll is associated with the stoppage of assimilation. Cells in 
which the green colour of the chlorophyll is quite masked by the 
presence of a brown or reddish-brown pigment, may show a distinct 
power of assimilation. In certain cases isolated chlorophyll-bcdies may 
continue to assimilate for a short time after removal from the cell to 
which they belong. 
Suction-Force of Transpiring Branches.* * * § — From experiments made 
on the transpiration of leafy and of leafless branches by means of 
Bourdon’s vacuum gauge, Prof. S. H. Vines has come to the conclusion 
that the imbibition-force of wood plays a more important part in the 
conduction of the transpiration-current than is at present generally 
admitted. On the whole, lie considers that Sachs’s imbibition-theory 
furnishes some, at least, of the essential elements of a complete explana- 
tion of the phenomenon. 
Influence of Temperature on Osmose.f — A series of experiments by 
the late Herr G. Krabbe, chiefly on the pith of the elder and of the 
sunflower, and on roots, lead to the conclusion that the rapidity of the 
osmotic process in living cells is materially affected by the temperature. 
The living parietal layer of protoplasm appears to possess the remark- 
able property of changing the size of the interstices between its micellae 
with changes of temperature. 
Influence of Climate and Soil on the Variation in Seeds f — As the 
result of a number of experiments, chiefly on wheat, M. E. Gain has 
established the law that it is by no means the richest soil that produces 
the most abundant crops. The optimum conditions for the species are 
not necessarily the most favourable for the individual. Both the number 
and the weight of the seeds will decrease when a plant is perpetuated 
year after year in the same locality. A change of soil is necessary for 
a permanent high rate of fertility. 
(3) Irritability. 
Mechanism of the Curvature of Tendrils.§— Mr. D. T. Macdougal 
gives the following as the more important results of his observation on 
a number of plants. The phenomenon is not due in all cases to the 
same cause. The curvature of stems, petioles and peduncles, in response 
to heliotropic and geotropic stimuli, is believed to be due to elongation 
of the convex sides of these organs ; while the movements of pulvini, 
of the tentacles of Drosera , and of the leaves of Dionsea are due to the 
action of cells on the side which becomes convex. The curvature of the 
tendrils of the Passifloraceae is due to the contraction of the tissues on 
the concave side. The curvature of a tendril round a support, as a 
direct reaction to irritation, and the coiling of a free portion, are distinct 
and independent processes. The region of maximum growth (in Passi - 
flora ) lies between the middle and the tip of the tendril, and never coin- 
* Ann. Bot., x. (1896) pp. 291-2, 429-44 (1 fig.). 
t Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxix. (1895) pp. 441-98. 
X Rev. Gen. de Bot. (Bonnier), viii. (1896) pp. 303-5. Cf. this Journal, 1895, 
p. 657. 
§ Ann. Bot., x. (1896) pp. 373-402 (1 pi.). Cf. this Journal, ante, p. 512. 
