ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
453 
and the ripening period. During this latter period an extended decrease 
(due to transpiration) lasting throughout the daily hours was quickly 
followed by the maximum increase. At the time of the grand maximum 
the fruit gained 782 grams in weight during 24 hours. The variations 
in length of the internodes occurred simultaneously with corresponding 
increase and decrease in the weight of the fruit. 
Growth of the Root.* * * § ' — Prof. W. Pfeffer corrects an erroneous state- 
ment in a previous publication, viz. that the growth in length of the 
apex of the root is promoted if growth is checked in the rest of the 
root. This statement was founded on erroneous observation. 
Dependence of the Leaf on its Power of Assimilation.f — From a 
series of experiments, chiefly on Phaseolus , Acacia , and Mimosa, Dr. L. 
Jost states that substances formed in the parts of a plant exposed to 
light may be used up, in the darkened parts, for the formation of new 
organs, or the development of those already formed. A leaf formed in 
the dark, and continuing in it, can, therefore, attain its normal develop- 
ment without itself assimilating ; while a leaf formed in the light will 
not unfold and become green in the dark, or in an atmosphere free from 
carbon dioxide. It follows therefore that the production of the chloro- 
phyll pigment is dependent directly on its power of assimilation, while 
the development of the leaf is only indirectly dependent on that 
process. 
Assimilation and Respiration.J — Mr. F. F. Blackman claims to 
have shown, by a new application of the baryta method of determining 
the amount of carbon dioxide exhaled by plants, that, under normal con- 
ditions, practically the sole pathway for carbon dioxide, in passing into 
or out from the leaf, is through the stomates ; although, under abnormal 
conditions, such as the closing of the stomates, a passage of the gas 
through the cuticle by osmose may take place. Isolated green leaves, 
when fully illuminated, allow no carbon dioxide to escape from them. 
The principal novelty in the process employed consists in the use of 
only a very small quantity of solution of baryta to absorb the carbon 
dioxide formed, the whole being titrated with acid in the tube in which 
the absorption has taken place. The plants experimented on were 
Ampelopsis hederacea, Bicinus communis , Alisma Plantago , and Iris ger- 
manica. 
(3) Irritability. 
Sensitive Movements under Coloured Screens.§ — As the result of 
a series of experiments on several plants with sensitive leaves ( Oxalis 
stricta and several species of Cassia ), Dr. J. M. Macfarlane somewhat 
modifies his previous view that the paraheliotropic movements of sensi- 
tive plants are due chiefly or entirely to the action of solar heat-rays. 
He finds the exciting agents to be certain of the light-rays. When 
sensitive plants are placed under coloured screens, the leaflets fold as 
in the nyctitropic state, most powerfully under red, less so under 
yellow, only feebly or not at all under green light, while under blue 
* Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxvii. (1895) pp. 481-3. 
t Tom. cit., pp. 403-S0 (1 pi. and 1 fig.). 
i Ann. Bot., ix. (1895) pp. 161-8; Proc. Roy. Soc., lvii. (1895) pp. 162-8. 
§ Bot. Centralbl., lxi. (1895) pp. 136-46, 177-84. Cf. this Journal, 1894, p. 593. 
