200 University of California Puhlications in Botany [Vol. 5 



seed, cotton seed, etc., suggested the possibility that similar 

 beneficial effects might be secured in the ease of tobacco seed by 

 similar treatment. As will be seen later on such has been found 

 to be the case in that treatment with 70 per cent or 80 per cent 

 sulfuric acid for lengths of time varying from five to fifteen or 

 twenty minutes markedly increases the total amount and in 

 many cases hastens the time of germination of the seed of a 

 number of species of Nicotiana. In the preliminary experiments, 

 seed of N. attenuata alone was used, but in order that the value 

 of sulfuric acid treatment might be further investigated in the 

 case of other species of Nicotiana it was first found to be neces- 

 sary to make germination tests with untreated seed to determine 

 the species which would give small total germination or slow 

 germination under experimental conditions. This, in a sense, 

 preliminary portion of the investigation has assumed rather large 

 proportions and a considerable mass of data is at hand that has 

 to do with the germination of seed of various ages derived from 

 single plants of eight species and varieties of Nicotiana and also 

 with the germination of hybrid seed obtained from crosses made 

 between certain of these species and between certain of these 

 varieties. Additional germination tests are at present under 

 way which are designed to demonstrate the possible wider use- 

 fulness of sulfuric acid treatment in taking the place of other 

 methods, peculiar to agricultural practice, of hastening the 

 germination of tobacco seed and increasing its amount. 



Detailed reports based upon definite germination tests in the 

 case of pure lines of Nicotiana species are not, to the writer's 

 knowledge, at present available. In general I think it has been 

 assumed, and probably correctly, that tobacco seed will give 

 rather high average total germination under field conditions and 

 that little difficulty is experienced by commercial growers of 

 tobacco in germinating the seed they use. The value of tobacco 

 seed separation and the greater uniformity and vigor of the 

 stand when only heavy seed, rather than mixed heavy and light 

 seed, is sown has been pointed out by Shamel (1904) and others, 

 while certain other more theoretical considerations in connec- 

 tion with the inheritance of certain characters in Nicotiana as 

 correlated with the weight of the seed used to produce the plants 



