ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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contain more, when stalked they contain considerably less water than 
green leaves of the same species. 
In another communication * * * § on the same subject, Prof. Palladin 
states that etiolated leaves (of wheat) which have grown to an 
abnormal length contain more water than those that are green ; while 
the reverse is the case with small leaves. The large young leaves near 
the apex of the stem, under the influence of light and transpiration, 
abstract water from the stem, which therefore grows slowly. In the 
dark, on the other hand, transpiration being arrested, the leaves do not 
grow so fast, while the stem grows faster. 
Ascending and descending Current in Plants.f — Herr J. Boehm 
adduces confirmation of his previous views on this subject from experi- 
ments on a sunflower cut down at the second internode. The capillary 
interstices of the soil and of the plant form a continuous system through 
which the water is conveyed to the transpiring leaves. When the soil 
is comparatively dry, and the sap-conducting vessels remain permanently 
filled with water, there must be a current of water descending from these 
into the soil. 
Internal Atmosphere of Tubers and Tuberous Roots. { — M. H. 
Devaux states that the exchanges of gases in tubers and tuberous roots 
are produced in three different ways, which ordinarily coexist: — (1) 
There is transmission by diffusion of free gases through the pores of 
the periderm-envelope, (2) Transmission by diffusion through the mem- 
brane, the gas being dissolved ; (3) Transmission by a strong gaseous 
current through the pores of the envelope. 
M. Devaux § further describes an apparatus which illustrates the 
gaseous changes that take place in a tuber. Briefly, it consists of a 
bell, the orifice of which is covered with a piece of vegetable parchment, 
and thus represents fairly well a tuber reduced to its external pellicle. 
It is then subjected to analogous conditions to those of the internal mass 
of the tuber, with the following results (1) When the membrane is 
dry, (a) the carbon dioxide increases in the internal atmosphere, (6) the 
oxygen penetrates by diffusion, (c) the nitrogen is in smaller proportion 
than in the external air, (d) the pressure of the internal gas is greater 
than that of the air. (2) When the membrane is wet, (a) the carbon 
dioxide diminishes rapidly, (b) the oxygen diminishes, (c) the nitrogen 
increases rapidly. 
(3D Irritability. 
Sensitive Stamens and Stigmas.|| —Prof. A. Hansgirg classifies the 
numerous examples of irritability in the stamens and stigmas which 
subserves the process of pollination, under the following five types, viz. : — 
(1) Cactacese- type: the numerous filaments are nearly equally sensitive 
on all sides, and curve centripetally, bringing the anthers towards the 
stigma ; the contractile parenchymatous tissue is well developed only in 
* Arb. Naturf.-Ver. Charkow, xxv. (1890) 5 pp. (Russian). See Bot. Centralbl., 
xlv. (1891) p. 279. 
f Ber. Deutsch. Bot. Gesell., viii. (1890) pp. 311-4, and SB. K. K. Zool.-Bot. 
Gesell. Wien, xl. (1890) pp. 55-6. Cf. this Journal, 1890, p. 632. 
X Bull. Soc. Bot. France, xxxvii. (1890) pp. 272-9. 
§ T. c., pp. 257-64. || Bot. Centralbl., xliii. (1890) pp. 409-16. 
