CHEMICAL SELECTION 01'' MOTHERS. 93 



in the same direction, otherwise there would result 

 considerable complication. 



Pellet makes some important observations respect- 

 ing the use of the Keil rasp. It should penetrate the 

 beet one-fourth of its length without neck. When 

 the cutting portions of the rasp are sharp and in good 

 condition, the pulp obtained is sufficiently fine to give 

 accurate results by the cold-water process of analysis, 

 but if the pointed rasp works badly the conditions are 

 changed. If the velocity of the rasp is too slow, or if 

 the motion is reversed, the pulp obtained is not suffi- 

 ciently fine for the purpose intended. It is important 

 to note that the hole made in the beet by the Keil and 

 Dolle rasp is 14 m. m. in diameter, that it in no way 

 destroys the keeping qualities of the mother root; also 

 that at least 300 perforations may be made per hour, 

 or 3000 a day; this cannot be reached at first and 

 requires considerable experience. To make sure of 

 conditions, a comparative test by cold and hot water 

 should be made. Place beside the rasp the tray hold- 

 ing ten capsules, or small receptacles for the reception 

 of the pulp. Each of them has' a number and the mix- 

 ing is done in them, or in a larger receiver. 



Weighing the Pulp. 



It is then emptied into a nickel capsule of a known 

 weight. It is desirable to have several on hand, so as 

 to avoid errors. The pulp, after being thoroughly 

 mixed, is weighed in capsules. One-quarter of the 

 normal weight required for the polariscope is sufficient 

 for the test; at least 1000 of such weighings can be 

 done in ten hours on ordinary scales, and for special 

 seed laboratories five or more scales are in active use. 



Filling of Flasks with Pulp. 



The flasks used have a capacity of 50 c. c. (Fig. 

 35), with a very large opening. The pulp is washed 



