ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
361 
increase in the width is most noticed, and the amount of the increase 
varies according to the distance of the trees which have been cut down 
from those reserved. 
Conduction of Water.* * * § — Herr F. Tschaplowitz describes a series of 
experiments which tend to the conclusion that air-pressure and capillarity 
play but a very subordinate part in the movement of water in plants, 
the really important factors being osmose and imbibition. The experi- 
ments were made chiefly on Spirwa opulifolia. 
Causes of the Ascent of Sap.f — Hr. J. Boehm adduces additional 
arguments in favour of his view that the absorption of water through 
the roots and the ascent of sap are the result of capillarity, the retention 
of the water in the parenchyme of the leaf being caused by the pressure 
of air. The objection that Conifers do not contain true vessels he 
answers by the statement that they do possess what are at least physio- 
logically equivalent to vessels. 
Literature of Transpiration. J — Hr. A. Burgerstein completes his 
resume of the literature of transpiration by an abstract of all papers on 
the subject published from 1887 to 1889. The paj^ers referred to are 
eight in number, and the whole subject (including “ guttation ” or the 
exudation of drops of fluid) is discussed under a number of different 
headings, reference being made to the conclusions arrived at by earlier 
observers. 
(3) Irritability. 
Nutation of Seedlings. § — Herr H. Molisch describes a new appa- 
ratus for demonstrating the hydrotropism of roots. It consists of a clay 
funnel with curved and perforated margin, filled with moist sawdust ; 
the roots of seedlings planted in it pass through the orifices, and grow 
upwards on the moist wall of the erect funnel. This form of nutation 
has received at present much less attention than the curvature of aerial 
shoots. 
Irritability of the Laticiferous tissue in Lactuca.||— Prof. F. Helpino 
has observed in Lactuca virosa and some other species of the genus, a 
singular extreme irritability. If, in the warm weather, the epiderm 
which covers the bracts and involucre is touched with an excessively 
delicate substance, not sufficient to rupture the epiderm, a minute drop 
of latex is suddenly shot out from the laticiferous tissue. This serves 
to explain the extraordinary immunity of these species of Lactuca from 
the attacks of insects. 
Galvanotropism.1T — From the results of a detailed series of experi- 
ments, Herr J. Brunchorst draws the conclusion that the curvature 
* ‘ Beitr. z. Lehre v. d. Wasserbewegung in d. Pflanze,’ 8vo, 8 pp. See Bot. 
Centralbl., xli. (1890) p. 149. 
t Ber. Ueutsch. Bot. Gesell., vii. (1889), Gen.-Versamml.-Heft, pp. 46-56 
(2 figs.). Cf. this Journal, 1886, p. 824. 
X Verhandl. K.K. Zool.-Bot. Gesell. Wien, xxxix. (1889) pp. 399-463. Cf. this 
Journal, 1888, p. 259. 
§ ‘Das Bewegungsverm6gen d. Keimpflanze,’ Wien, 1889, 8vo, 27 pp. and 7 figs. 
See Bot. Centralbl., xl. (1889) p. 214. 1| Malpigbia, iii. (1889) pp. 355-7. 
^ ‘ Notizen lib. d. Galvanotropismus,’ Bergen, 1889, 8vo, 35 pp. See Bot. Cen- 
tralbl., xli. (1890) p. 257. Cf. this Journal, 1886, p. loi. 
