so 



Elementary Plant Physiology. 



instances, and thus determine the influence of concentration 

 upon osmotic attraction. Root-hairs contain sugars and acids, 

 and act in much the same manner as these dialyzers. 



This demonstration may also be made by the use of the 

 following material : secure a cylindrical lamp chimney, and 

 fasten a piece of well-soaked bladder or parchment over the 

 larger end. Support in a large cylinder, as in Fig. 26. 

 Fill the lamp chimney one-third full of moist sugar, and pour 



water in the cylinder until it rises 

 to the level of the sugar. Observe 

 results an hour and four hours 

 later. Make a second test with 

 a weak solution of sugar. 



45. Osmose in plant tis- 

 sues — Secure a long potato 

 tuber, and bore a hole from one 

 end nearly to the other, about two 

 centimeters in diameter. Peel 

 the closed end of the potato care- 

 fully, over an area extending 

 about 5 cm. from the closed end, 

 and cut the end squarely across, 

 so that the tuber will stand up- 

 right on this end as a base. Care 

 must be taken that the tuber is 

 Now set the tuber upright in a 

 shallow dish containing sufficient water to immerse all of 

 the peeled surface. Fill the cavity with granulated sugar to a 

 depth of about six or eight centimeters. Add enough water to 

 saturate the mass of sugar. Set aside for a few hours. The 

 sugar in the cavity will draw water from the living cells nearest 

 it, and these in turn will draw water from the next layer, by 

 reason of their superior concentration of cell sap ; and so on to 

 the outer layer of the potato, which takes in water from the 



Fig. 27. — Potato osmometer. 

 The lower end of a potato is pared, 

 and set in a disli of water. A 

 central cavity is made, "which is 

 filled with sugar. 



not cracked or pierced. 



