ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
71 
Assimilation and Respiration.* * * § — Prof. Kreusler has determined, 
from experiments chiefly on the bramble and cherry-laurel, that the 
optimum temperature for the exhalation of carbon dioxide is about 45° 0., 
a rise of 5° above this showing a considerable diminution in the energy 
of the respiration ; he finds no confirmation of the theory of a “ post- 
mortal ” respiration. The assimilating energy shows no considerable 
variations between 15° and 30° C. ; above 30° it begins gradually to 
diminish, falling to zero at a temperature between 45° and 50° C. 
Assimilation by Red Leaves.f — From observations on the red 
varieties of the beech, the birch, and the sycamore, M. H. Jumelle 
concludes that in trees with leaves of a red or copper colour, chloro- 
phyllous assimilation is always less intense that in the same trees with 
green leaves ; in the case of the copper-beech and purple sycamore, this 
is reduced to one-sixth of the normal amount. 
Influence of high altitudes on Assimilation and Respiration. :J — 
As the result of a series of experiments on a number of species, chiefly 
herbaceous, Prof. G. Bonnier finds that in the same plants, placed in the 
same external conditions, the specimen grown in an alpine climate modifies 
its functions by the augmentation of chlorophyllous assimilation and 
transpiration, while respiration and transpiration in the dark appear to 
be scarcely affected by the change. 
Permeability of Wood to Air.§ — M. Kruticki distinguishes in this 
respect three classes of wood, viz. (1) Those which present great 
permeability, as the oak and poplar, in which the air can penetrate 
under a pressure of from 3 to 10 mm. of mercury; (2) Those of low 
permeability, like the birch and maple, which require a pressure above 
that of the atmosphere ; and (3) Those of moderate permeability, which 
are very numerous. The air contained in the branches has not always 
the same composition ; in winter it contains less oxygen than the atmo- 
spheric air, but a larger proportion of nitrogen, and especially of carbonic 
acid ; with the commencement of spring, the proportion of oxygen 
increases, while that of carbon dioxide diminishes, so that when the buds 
expand, the composition of the imprisoned air is very nearly that of the 
atmosphere. 
C3) Irritability. 
Action of Water on Sensitive Movements.|| — M. H. Leveille gives 
the details of an experiment on this point with Mimosa rubricaulis ; 
the following conclusion was arrived at : — plants, if placed under water, 
retain their sensitiveness as long as they retain any vigour. 
Movements of the Leaves of Porlieria hygrometrica.1T — Dr.G. 
Paoletti states that the diurnal movements of the leaves and leaflets of 
this plant (Zygophyllacese) is due to unequal turgidity of the two cells 
* SB. Niederrhein. Gesell. (Verhandl. Naturhist. Ver. Preus. Rkeinl.), lxxiv. 
(1890) pp. 54-60. 
f Comptes Rendus, cxi. (1890) pp. 380-2. 
% T. c., pp. 377-80 ; cf. this Journal, 1890, p. 486. 
§ Script. Bot. Hort. Univ. Imp. Petropolitame, ii. See Bonnier’s Rev. Gen. de 
Bot., ii. (1890) p. 324. || Bull. Soc. Bot. France, xxxvii. (1890) p. 153. 
II Malpighia, iv. (1890) pp. 31-40. 
