748 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Descending Transpiration-current.* * * § — Prof. J. Wiesner finds that if 
Capsella bursa-past or is, Beilis perennis, or Sempervivum tectorum is grown 
in air completely saturated with moisture, the habit of the plant is 
altered by the greatly increased development of the internodes of the stem. 
Taraxacum officinale, on the other hand, appears to undergo no change 
under similar conditions. 
Ascent of Coloured Liquids in Living Plants. j* — Herr F. Goppels- 
roeder has investigated the phenomena connected with different coloured 
fluids in a number of different species of plant. When very dilute he 
states that a large number of such pigments may pass into the plant 
without apparent injury. The rapidity and extent of this circulation 
varies with the species of plant and with the pigment employed, some 
pigments rising to the very summit of the plant, while others again 
are not absorbed at all. 
Prof. G. L. Goodale J contests the statement of Goppelsroeder that 
coloured fluids can be absorbed in this way without any disturbance to 
the plant itself. Plants with injured roots can live and grow slowly 
for a considerable time. 
(3) Irritability. 
Conduction of Irritation in the Sensitive Plant. § — From a series 
of experiments on Mimosa pudica, Hr. G. Haberlandt shows the untena- 
bility of the conclusion drawn by previous observers that the irritability 
of the leaves of the sensitive plant is conducted mainly through the 
xylem portion of the vascular bundles. He demonstrates, on the 
contrary, that the stimulus normally travels inside the zone of collen- 
chyme or bast-fibres, but outside the xylem of the bundles, and therefore 
through their phloem portion. When a stem is cut through, drops 
exude from the cut surface, and these can be shown to arise, not from 
the xylem, but from special cells in the phloem. This special conducting- 
tissue is described by the author for the first time. It consists of rows 
of cells, somewhat larger than the ordinary phloem-cells, in the trans- 
verse wall of each of which is a single large shallow pit, traversed by 
very delicate protoplasmic filaments. The contents of these cells is a 
crystallizable substance, probably a glucoside ; they replace the tannin- 
sacs of other Leguminosas. These special cells form a part of the 
phloem, from the pulvinus at the base of the leaf to the larger bundles 
in the leaflets. Dr. Haberlandt believes that the protoplasmic filaments 
which penetrate the pits in the walls of these cells, play but a small 
part in the transmission of the irritation; it is conveyed in a purely 
mechanical manner from the pulvinus, as a wave or impulse passing 
along the glucoside-containing cells. 
Sleep of Leaves. || — M. Leclerc du Sablon states that it is well 
known that the leaves of certain plants, under the influence of external 
conditions, can take up different positions. For example, in Oxalis 
* Yerhandl. K.K. Zool.-Bot. Gesell. Wien, xl. (1890) SB., p. 30. 
f ‘Ueb. Capillar-analyse u. ihre verschiedenen Anwendungen,’ Wien, G5 pp. 
See Bot. Ztg., xlviii. (1890) p. 345 % Amer. Journ. of Sci., xl. (1890) p. 173. 
§ ‘ Das reizleitende Gewebe d. Sinnpflanze.’ Leipzig, 1890, 87 pp. and 3 pis. 
See ‘ Nature,’ xlii. (1890) p. 501. 
|| Rev. Gen. de Bot. (Bonnier), ii. (1890) pp. 337-40. 
