210 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
(3) Irritability. 
Twining of Climbing Plants.* * * § — Dr. F. Noll points out that a twining 
or climbing plant attains the same object of exposing its leaves and flowers 
freely to the air, at far less expense of material than a plant with a stout 
woody stem. Hence it has more energy to spend in providing material 
for its often very large leaves and handsome flowers. 
Mechanism of Curvature in Plants.f — Dr. W. Rothert criticises 
Herr Kohl’s new theory on this subject. The essence of Kohl’s theory 
lies in the fact that he attributes the process of curvature to an increased 
turgidity of the cells of the side which becomes concave, resulting in an 
active shortening of these cells. The active part of the process is thus 
confined to the concave side, the convex side is merely passively 
stretched, and curvature is thus primarily independent of growth. 
Rothert opposes the theory, because it assumes that the mechanism of 
curvature is different in unicellular and in multicellular organisms, and 
also because of the difficulties connected with a passive stretching of the 
convex side. The remainder of the paper is devoted to a detailed 
criticism of Kohl’s statements, Rothert’s conclusion being that, although 
Kohl has brought forward some new points of interest, his theory as a 
whole is untenable. 
(4) Chemical Chang-es (including: Respiration and Fermentation). 
Accumulation of Sugar in the Beet-root.| — M. L. Maquenne attri- 
butes the relation between the amount of sugar in the leaves and in the 
root of the beet to the operation of the principle that osmotic pressure is 
in inverse proportion to the molecular weight of the dissolved substance. 
The molecular weight of saccharose is double that of glucose. When, 
therefore, in consequence of assimilation, the osmotic pressure increases 
in the leaves, the elaborated principles take the form of saccharose and 
move towards the root ; when the pressure in the leaves diminishes, the 
sugar of the root undergoes deduplication and moves towards the 
leaves ; while, when the pressure remains constant, all movement 
ceases. 
7 . General. 
Temperature of Trees.§ — Mr. R. W. Squires has made a series of 
experiments on the temperature of a trunk of Acer Negundo between 
January and June. He finds that, as a general result, the temperature 
of the tree is lower than that of the air in the morning and at noon, 
while it is higher in the evening. The mean temperature of the tree, as 
compared with that of the air, was 1*31° C. higher in January, in 
February nearly the same, in March nearly 1° lower, in April 0 • 85° 
higher, and in May 1 * 13° lower. 
Dippel’s Microscope and its Application, Part II.|| — The first divi- 
sion of the second part of the second enlarged edition of this important 
* SB. Niederrhein. Gesell. Natur- u. Heilkunde Bonn, 1895, pp. 15-7. 
t Biol. Centialbl., xv. (1895) pp. 593-602. Cf. this Journal, 1895, p. 455. 
X Comptes Ilendus, cxxi. (1895) pp. 834-7. 
§ Minnesota Bot. Studies, 1895, pp. 452-9. 
|| ‘ Das Mikroskop u. seine Anwendung,’ 2 te umgearb. Auflage, 2 ter Th., l te Abth., 
Jena, 1896, 443 pp., 3 pis. and 302 figs. 
