112 ILLINOIS STATE ACADEMY OF SCIENCE 



The problem of finding how much growth, due solely to 

 the reserve food in the seed, will take place in seedlings from 

 seeds separated according to specific gravity and to size has 

 not, as yet, been studied. The solution of this problem is 

 the object of the experiments here recorded. 



II. MATERIALS AND METHDOS 



(1) Selection and Separation of the Seed Used. 

 The common garden bean because of its ready adapt- 

 ability to laboratory conditions was chosen for these ex- 

 periments. In the spring of 1919, ten pounds of Burpee's 

 Red Valentine seed of the season of 1918 were divided ac- 

 cording to their specific gravity into six groups. This 

 separation was made by means of solutions of chemically 

 pure sodium nitrate dissolved in distilled water. A prelimi- 

 nary test showed that few seed sank in a solution of 1.32 

 specific gravity, or floated in one of 1.12. The solutions 

 used consequently range from 1.32 to 1.12 specific gravity. 

 They were prepared with the use of a Twaddell hydrometer, 

 corrected for 60° F., and both seeds and solutions were kept 

 at this temperature while testing. The solutions made up 

 differed from each other in specific gravity by .05 and, in 

 use, were not allowed to vary by more than .005. 



A few seeds were placed in a small tea strainer, dipped 

 into 95 ^'f alcohol to remove the air film and then transferred 

 to a larger strainer immersed in a solution of sodium nitrate 

 of 1.32 specific gravity. The seeds which floated were re- 

 moved by a second small strainer and they as well as the 

 ones which sank were rapidly and thoroughly washed, and 

 spread out on towels in a warm room to dry. The ones 

 which sank, after drying, were stored in glass jars for 

 future use. After all the seeds had been passed through 

 the solution of greatest density (1.32 sp. gr.), those 

 which floated were taken in a similar manner through the 

 solution next lower, solution of 1.27 sp. gr., etc. By this 

 method six groups of seeds were obtained. These groups 

 are designated in the discussion and in the tables as follows : 



Density 1, seeds which sank in a solution of 1.32 sp. gr. ; 



Density 2, seeds which sank in a solution of 1.27 sp. gr. ; 

 (range from 1.32-through 1.27) ; 



