1913] Goodspeed: Nicotiana Ilyhrids 191 



germination tests of parent and hybrid tobacco seed involving 

 over 22,000 seeds and including over 10 species and varieties of 

 Nicotiana (Goodspeed, 1913 (2)). These germination tests deal 

 with the seed taken from approximately 60 different plants. It 

 was possible to fairly well control the conditions under which 

 germination took place and the arrangement of the seed to be 

 germinated was such that a minimum error for the observations 

 can be claimed. In only one case, however, employing duplicate 

 tests for the seed of each plant, did 100 per cent germination 

 take place. In the case of the seed of one other plant one of the 

 two tests of 100 seeds each germinated 100 per cent, but in the 

 other test of this same seed only 97 per cent germination took 

 place. Thus there seems to be some reason to doubt whether 

 100 per cent germination is normal in the case of seed produced 

 by Nicotiana species and varieties or by the hybrids made between 

 them. Unfortunately it has not at this time been possible to 

 test the germination of the seed produced by the crosses between 

 N. sylvestris and N. Ta6flcwm-varieties mentioned in the above 

 tabulation. In general, however, it is well to understand what 

 is meant when germination percentages are given. 



There are a number of references in the literature to the 

 sterility in F^ of species crosses involving N. sylvestris as a 

 male or female parent (cf. East and Hayes, loc. cit., p. 28; 

 Baur, 1911, p. 224). On the hybrids, mentioned above as 

 being made in 1910 and growing in 1911, no "pure" seed was 

 formed under bag so far as was determined at the time and 

 indeed all maturing seed capsules that were protected fell long 

 before the calyx had begun to wither or the ovary turn brown. 

 Twenty or thirty shrunken but dried ripe seed capsules from 

 unprotected flowers were collected from the plants of this H33 

 cross and its reciprocal (H34). These capsules were "cleaned" 

 (Goodspeed, 1912, p. 129) carefully but no seed was found. The 

 contents of one seed packet resulting from this "cleaning" was 

 sown on the possibility that a few viable seeds might be j)resent 

 and have been overlooked, but no seedlings resulted. 



A considerable amount of attention has been given this year 

 to the phenomenon of sterility in the F^ hybrid plants grown 

 from the hybrid seed resulting from the 1911 crosses. The most 



