CHEMICAL SELECTION OF MOTHEKS. 115 



14 per cent, sugar are taken to a second laboratory, 

 where other chemists continue the work. The 2 c. c. 

 of juice remaining from the sample above referred to 

 (the total volume being 6 c. c), are thoroughly defe- 

 cated in a Stammer oven (4), heated by steam. The 

 weight of dry substance and the sugar percentage give 

 the purity coefficient. If this purity coefficient is 

 higher than 85, the beet is perforated for the second 

 time, and with the new sample of pulp obtained, the 

 Soxhlet-Sickel (5) extractor allows one to determine 

 very accurately the sugar percentage. 



In 1890, instead of obtaining the juice under pres- 

 sure and extracting by alcohol (6), the cold-water proc- 

 ess demanded the use of the Keil rasping method (7, 8 

 and 9). Fifteen grams of pulp are thus obtained; one- 

 half of normal weight are weighed, and the sugar per- 

 centage is determined as previously described. It is 

 admitted that this French method has made the work 

 much simpler, an<j the results are more satisfactory. It 

 is not necessary to enter into other details regarding 

 this laboratory, as there are several of the same 

 importance in many beet-seed pnoducing centres of 

 the country. 



Polariscopes for Mother Selection. 



The type of polariscope for selection of mothers 

 should not be the same as that used for sugar polari- 

 zations, where the right-hand polarizations reach 100 

 degrees. As the tubes used in the beet-seed selecting 

 laboratories are 400 m. m. in length, and as only 

 i6.29-=-4 grams of pulp are used at a time, it is prefer- 

 able to have the vernier graduated only to 25 degrees, 

 for example, and at the other end starting from 

 12 degrees. 



The plan of having a special electrical attachment 

 to the vernier of a polariscope is very simple, and has 

 rendered considerable service. The adjustment in 



