ABSORPTION OF LIQUID NUTRIMENT. 



17 



■containing water. The contents of the cylinder increase in volume 

 by absorption of water, and the membranes take a convex form 

 in consequence of the increased pressure inside the cylinder. 

 Place the cylinder in a vertical position and pierce the upper mem- 

 brane with a needle. The liquid spurts upward from the pressure. 



(Fig. 12.) 



Fig. 12. 



Artificial cell to illustrate force of turgor. (After Oels.) 

 EXPERIMENT 21. 



IMBIBITION (osmose) OF WATER BY SEEDS. 



Ascertain the exact weight of 20 dried Peas, and place in a 

 dish containing distilled water. In 24 hours the Peas will have 

 greatly increased in size by the diffusion of water through the 

 seed-coat. The substances stored in the seed have a strong attrac- 

 tion for water. Dry the seeds by rubbing with a cloth, and weigh. 

 In some cases they will have taken up their own weight of water. 

 The force of the osmose may be shown if a bottle of 25 cc. capacity 

 is filled with the seeds and immersed in a vessel of water for 24 

 hours. 



EXPERIMENT 22. 



LONGITUDINAL TISSUE-TENSIONS. 



Cut a slice a centimeter in thickness and 10 cm. in length 



Fig. 13. 



Longitudinal tissue-tensions. (Hansen.) a, outward curvature of a sec- 

 tion due to excess of turgor of pith ; b, length of separated tissues ; 

 m m, pith (parenchyma). 



