1912] Goodspeed: Xicotiana Hybrids 95 



for the heavy grades was discarded and also the very minute 

 seeds noted above as having occurred among the heavy grades — 

 64 seeds in the first case and 80 seeds in the second, out of 

 400 seeds examined. The remaining seed was fairly uniform 

 in size and distinctly smaller than the heavy seed. Among the 

 light seed, which had been taken from box two, the 

 greatest number of ill-formed seed occurred and also twenty 

 per cent of the minute seed — -this on the basis of twelve hundred 

 seeds examined. It was found possible to separate out these 

 very small seeds and still have a light grade of seed that was 

 distinctly set apart from the medium seed in size and was about 

 one-half the size of the heavy grade. From the various grades 

 and the ill-formed seed a total of 2200 seeds, in separate packets 

 of 100 each, were counted out preparatory to weighing. 



The scales used were the mechanical balances manufactured 

 by Josef Nemetz of Vienna and weighing from 0.0001 of a 

 gram to 1 gram only. Since more delicate balances were not 

 available, it was necessary to weigh the extremely small tobacco 

 seed by hundreds and then by tens. The following table gives 

 the weights of the various grades of seed, as divided by the 

 air-blast, in terms of 100 seeds for each number and thus really 

 expresses the average weiglit of groups of 100 seeds from 

 each grade. 



Ill-formed seed Light seed Medium seed Heavy seed 



1. 0.0042 3. 0.0044 7. 0.0063 13. 0.0086 



2. 0.0041 4. 0.0057 8. 0.0064 14. 0.0091 



5. 0.0059 9. 0.0065 15. 0.0094 



6. 0.0061 10. 0.0067 16. 0.0095 



11. 0.0070 17. 0.0095 



12. 0.0073 18. 0.0097 



19. 0.0098 



20. 0.0099 



21. 0.0099 



22. 0.0111 



In each case the 100 seeds were counted into the pan of 

 the balances — picking up each seed with a brush — weighed, then 

 removed and weighed again by tens. The weights of the groups 

 of ten seeds were, with the exceptions noted below, in every 

 case found to be so nearly the same that it was felt, by ex- 



