324 The Botanical Gazette. [August 
ion, it is no doubt remembered that Sachs viewed the matter 
thus: ‘‘Jede Kraft, welche sehr langsam und continuirlich 
ein Austreten des Wassers im Sinne der Imbibition bewirkt, 
kann die Krystallbildung beférdern, solche Kriifte sind die 
Contraction des Gewebes, der von den Wurzeln aus stattfind- 
ende Saftdruck.” The older experiments of Sachs, as wellas ; 
the latest investigations of Strasburger and especially of _ 
Schwendener® show that we know very little of the means by — 
which water ascends to the middle and the higher parts of trees. _ 
Yet sheet-crystals are found at a considerable distance from 
the bases of the stems. As to the specific variations sut- 
mised by Atkinson, no record of experiments concerning | 
them can be found in my lists of literature. : 
Capillary forces alone would hardly be able to supply the ; 
crystals, especially those on branches of trees, etc.; the old 
experiments by Montgolfier and Jamin, and the numerous [a , 
ter experiments with Jamin’s chain prove this. It is well 
known that in capillary spaces filled with air and water, the 
latter does not move to any great extent. : Saye 
For these reasons, and from the above mentioned free 
ing experiment, it becomes evident that the exudation 
water from cut surfaces is in the first place caused by beg 9 
traction of the cells and tissues; we further know pee 
produces a power of filtration in the membranes gre a 
under normal conditions of temperature. In cold, ie a 
very slight pressure will be necessary to make the flui f a 
pear at the ends of the wood. As far back as 1859, 
: ha that any 
these forces js unknown, it is most safe to Saj h the stem? 
agency which is able to force water upwards throug: 
can supply the ice-crystals with water. 
arenes ayes ishiusivuibiess_oomsneniassionncie niall aie . ain, 
*Sitzungsberichte der Akademie der Wissenschaften zu anne 
and ibid, October 26, 1893.—I may add that it is four y en the 
Conte’s Paper; at present I have access only to the phadasgsiey ik 
Scientific Discovery,’’ ed. by D. A. Wells, Boston 1851, P- 
