110 University of California Puhlications in Botany [Vol. 5 



the 1906 and 1907 virginica seed was somewhat slower. At the 

 end of nine days there was no sign of germination and after 

 sixteen days 68 per cent of the 1906 and 71 per cent of the 

 1907 seed had germinated. The total germination after 20 days 

 showed that 



1906 — virginica seed germinated to the extent of 81 % 



1907 — virginica seed germinated to the extent of 88 % 



1907 — macropliylJa seed germinated to the extent of 91 % 



The appearance of mould about the seed that had not germinated 

 necessitated a termination of the experiment at the end of 

 twenty days. 



This parental seed was, as before noted, indiscriminately 

 chosen and showed throughout a marked uniformity in size and 

 shape of individual seeds. That within less than three weeks 

 such a high percentage of germination should have taken place 

 among the relatively old parental seed (Shamel and Cobey, 1906, 

 p. 35, Hayes, 1912, p. 3) is interesting and also somewhat unex- 

 pected when we recollect the results obtained in germinating the 

 hj'brid F^ seed. 



That the parental seed possesses a considerably greater degree 

 of uniformitj^ in shape, size and weight than does the hybrid 

 seed is, in general, shown by its appearance under the lens, in 

 particular by the close agreement between the weights of various 

 samples of the seed, and finally by the fact that its germination 

 was fairly simultaneous within each group. In other words, 

 there seems to be sufficient evidence to warrant the statement 

 that for the parental seed there is no such distinct and well- 

 marked division into grades according to physical characteristics 

 as was found in the hybrid seed of a plant produced by crossing 

 these parents. 



The facts of greatest significance in connection with the ger- 

 mination of the difi:erent divisions of F^ hybrid tobacco seed 

 according to weight are (1) that the seedlings in the rosette 

 stage — i.e., sufficiently developed to be set out in the field — 

 showed a superiority of vigor for the young plants grown from 

 heavy seed over those grown from light seed, and (2) that at 

 the period of maturity the number of plants fully grown and 

 normally developed which had been produced from light seed was 



