CAUSES OF THE MOTIOX 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., g 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, 

 , is closed in similar manner by a piece of parch 

 ment-paper, (p. 59.) Finally a cap of India- 

 rubber, If, into whose neck a narrow, bent glass 

 tube, r, is fixed, is tied on over b. (These join 

 ings must be. made very carefully and firmly.) 

 The space within r JTis left empty of liquid, and 

 the combination is placed in a vessel of water, as 

 in the figure. C represents a root-cell whose 



exterior wall (cuti 

 cle,) a, is less pene 

 trable under pressure 

 than its interior, b ; 

 r corresponds to a 

 duct of vascular tis 

 sue, and the sur 

 rounding water takes 

 the place of that 

 existing in the pores 



Fig. 69. 



of the soil. The water shortly penetrates the cell, (7, 

 distends the previously flabby membrnnes, under the ac 

 cumulating tension filters through b into r, 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 b, 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 c* 

 very satisfactory glance into the causes of bleeding. 

 16 



