620 
Physiologie. 
\ 
which had killed itself by taking up the formalin, but that it 
travelled in the older inner still living wood which the lirst current 
of formalin had not touched. 
The author holds that the part played by the living cells in 
wood is not a direct “pumping” action but that these cells continually 
restore the favourable conditions for the ascent of water wherever 
these are affected by the excessive emptying of the vessels and keep 
down the resistance to flow by maintaining continuous water 
columns in parts of the wood. 
The bleeding of roots and stems is not a final proof that vital 
pumping action goes on, since all the observed cases can be 
explained as al result of osmotic action coupled with a reabsorption 
of the osmotic material from the ascending stream, of which the 
first stage would be ad'sorption of the material by the walls of the 
vessels. How the living cells actually work is as yet unknown. 
Experimental measurements were made of the positive or 
negative pressures in trees at various distances from the ground 
and also of the effect of suction or injection at one branch upon the 
manometers attached to other branches. This work showed consi- 
derable isolation of the various regions and all pointed against the 
existence of continuous suspended water columns or high internal 
tensions in the conducting elements. 
The same was indicated by direct measurements of the pressure 
in intact vessels of Wistaria during active transpiration. Probably 
the high resistance to flow of w T ater is overcome locally, from point 
to point, and not by enormous suction from above, which leads to 
inflow of air and rapid blocking; or by high pressure from below, 
which leads to great loss by lateral exudation from the vessels. 
Ewart accurately measured the tallest Eucalyptus trees in 
Australia and found none over 303 feet though many had been 
reputed to exceed 400 feet. This reduces the maximal total resistance 
to upward flow in tallest trees to between 30 and 50 atmospheres. 
The energy required per diem to lift the water supply in such 
a tree could all be obtained by the combustion of a small amount 
of the carbohydrate formed in photosynthesis. Ewart calculates that 
J to 1% of the daily assimilation would suffice. The pumping action 
required is therefore but feeble in intensity and diffuse in character 
and it is just these characters which render its direct demonstration 
so difficult. F. F. Blackman. 
Fitting, H., Die Reizleitungsvorgänge bei den Pflanzen: 
I. Teil. Das Vorkommen von Reizleitungsvorgängen bei 
den Pflanzen und die Methoden zu ihrem Nachweise. 
(Ergebnisse derPhysiol., hsgb. von L. Asher und K. Spiro. 4. Jahrg. 
I. II. Abt. Wiesbaden, p. 684—763. 1905.) 
In dem vorliegenden Sammelreferat ist die Litteratur des im 
Titel genannten Themas in mehr als 250 Nummern zusammen¬ 
gestellt und der Stoff nach folgender Anordnung dargestellt: 
Reizleitungen werden getrennt in solche die durch Aussen- 
und die durch Innenreize veranlasst werden. (Abschnitt 1 und 2.) 
Solche bei vielzelligen Pflanzen werden von denen bei einzel¬ 
ligen geschieden. Die differenten Reize selbst, die gesondert be¬ 
trachtet werden sind im I. Abschnitt: 
Stossreize (Mimosaceen, Oxalidaceen, Ranken, Dionaea, Aldro- 
vanda, Blütenteile), Kontakt- und chemische Reize (Drosera 
