CAUSES OF THE MOTION OF JUICES. 361 
cambial tissue, and when new, are very delicate in their walls. 
Fig. 69 represents a simple apparatus by Sachs for imi- 
tating the supposed mechanism and process of Root-ac- 
tion. In the fig., gy g represents a short, wide, open glass 
tube; at a, the tube is tied over and securely 
closed by a piece of pig’s bladder; it is then 
filled with solution of sugar, and the other end, 
b, is closed in similar manner by a piece of parch- 
ment-paper, (p. 59.) Finally a cap of India- 
rubber, -, into whose neck a narrow, bent glass 
tube, 7, is fixed, is tied on over 6. (These join- 
ings must be made very carefully and firmly.) 
The space within r “is left empty of liquid, and 
the combination is placed in a vessel of water, as 
7 in the figure. C' represents a root-cell whose 
exterior wall (cuti- 
cle,) a, is less pene- 
_trable under pressure 
than its interior, 6 ; 
r corresponds to a 
duct of vascular tis- 
sue, and the sur- 
rounding water takes 
the place of that 
exjsting in the pores 
of the soil, The water shortly penetrates the cell, C, 
distends the previously flabby membranes, under the ac- 
cumulating tension filters through 6 into 7, and rises in 
the tube; where in Sachs’ experiment it attained a height 
of 4 or 5 inches in 24 to 48 hours, the tube, r, being about 
5 millimeters wide and the area of +d,'700 sq. mm. When 
we consider the vast root-surface exposed to the soil, in 
case of a vine, and that myriads of rootlets and root-hairs 
unite their action in the comparatively narrow stem, we 
must admit that the apparatus above figured gives us a 
yery satisfactory glance into the causes of bleeding, 
16 
