CAUSES OF THE MOTION OF JUICES. 



361 



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cambial tissue, and when new, are very delicate in their walls. 

 Fig. G9 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 , 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, K, 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 -ZTis 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 f 

 r corresponds to a 

 duct of vascular tis- 

 sue, and the sur- 

 rounding water takes 

 the place of that 

 existing 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 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 , 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, wo 

 must admit that the apparatus above figured gives us a 

 very satisfactory glance into the causes of bleeding. 

 16 



