ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
221 
•stances, mostly of the nature of glucose. Sometimes they contain air or 
some other gas. 
The sensitive organs chiefly observed were : — The stigma of Martynia , 
Mimulus, Bignonia, Tecoma , &c. ; the stamens of Portulaca grandiflora, 
of Opantia amyclea , and other Cactaceae, and of the Berberideae ; the 
leaves of Mimosa. 
Positive and Negative Heliotropism.* — Herr F. Oltmanns confirms 
his previous statement of the existence of au optimum intensity of light 
for heliotropic curvatures for each species. With the fructification of 
Phy corny ces he found the curvature to be negative, indifferent, or positive, 
according to the distance from the source of light ; the former being the 
case when the distance is least, the latter when it is greatest. Green 
barley seedlings were more sensitive to light than etiolated ones. The 
horizontal position of many stems and aerial stolons is the result of 
purely geotropic causes, often entirely uninfluenced by light. 
Aerotropism of Roots.f — Dr. A. J. Ewart gives further examples of 
the aerotropic, or, as he prefers to term it, the oxytropic irritability of 
the apices of roots. This property is especially well marked in seed- 
lings of Rcliantlms , Cucurbita , and Pisum ; but it is probably very 
general. 
(4) Chemical Changes (including Respiration and Fermentation). 
Formation of Proteids in Plants.^ — According to Herr T. Kosu- 
tany, leaves contain a somewhat larger amount of nitrogen by night than 
by day ; there are then also more amraoniacal salts, and as large a propor- 
tion of proteids. There is, on the other hand, a larger amount of nitrates 
in the daytime ; from which it would appear probable that the nitrogen 
of nitrates is converted into proteids more by night than by day. No 
asparagin could bo detected in the night, being probably converted into 
proteids. The nett result is that the raw materials for the production 
of proteids are absorbed by the plant in greater quantities during the 
day, but that the final process takes place chiefly at night. 
Formation of Non-nitrogenous Reserve-Substances in the Almond.§ 
— From a series of analyses of almonds made at different stages of their 
ripening, M. Leclerc du Sablon draws the geueral conclusion that, as 
the amount of oil increases, that of the fatty acids diminishes, the former 
being apparently formed at the expense of the latter. Glucose is, in the 
same way, used up in the formation of the reserve food-materials; sac- 
charose, on the other hand, being found only in the ripe seed ; the same 
is the case also with the amyloses. 
Evolution of Heat by Wounded Plants. || — Mr. H. M. Richards 
gives further results of his experiments on the effects of mechanical 
injury on potatoes, onion bulbs, and other structures, with a description 
of the apparatus used to measure the rise in temperature. He finds in- 
variably a rise in temperature of the adjacent tissue, which attains its 
* Flora, lxxxiii. (1897) pp. 1-32. Cf. this Journal, 1892, p. 513. 
t Proo. Liverpool Biol. Soc., x. (189G) pp. 190-3. 
j Landwirthsch. Versuclis-Stat., xlviii. (1896) pp. 13-33. See Bot. Centralbl., 
1890, Beih., p. 488. § Comi-tes Rendus, cxxiii. (1896) pp. 1084-6. 
|1 Ann. Bot , xi. (1897) pp. 29-63 (2 figs.). Cf. this Journal, ante, p. 145. 
