1919] 



Goodspcecl: Germination of Tobacco Seed 



453 



g-ermiiiated seeds picked out. The criterion of germination was the 

 same as that noted in a previous paper. 



The breeding experiments with Nicotiana conducted in the Univer- 

 sity of California Botanical Garden cover a considerable number of 

 years ; thus we will be able to investigate the light requirements for 

 germination in the case of seed of various ages. Attention might 

 again be called to the fact that the seed used in our experiments is 

 pedigreed seed representing in each ease the product of individual 

 plants of species and varieties of Nicotiana grown in the pure line. 

 The writer's previous reports have indicated the remarkable viability 

 of old tobacco seed. In the table below it will be noted that in the 

 case of the N. Tahacnm varieties seed varying in age from nine to twelve 



^ The figures in bold face type refer to seed germinated in continuous darkness. 



' TTp to this point the figures in ordinary type refer to seed gennination in continuous 

 light, the source of light being a 40-watt tungsten electric light bulb. The remaining figures 

 in ordinary type refer to seed germinated under diurnal illumination. 



■■ "-)-" indicates that the per cent of seeds germinated in darkness e.xceeded the per cent 

 germinated under continuous or diurnal illumination. 



■• " = " indicates that germination under the two conditions was the same, a difference 

 of less than ten seeds being the criterion. 



° " — " indicates that germination in darkness was decidedly less than under continuous 

 or diurnal illumination. 



