206 University of California Publications in Botany [Vol. 5 



From the above figures it is evident that treatment with 80 per 

 cent sulfuric acid for lengths of time not much greater than 

 ten minutes will materially increase the amount of total ger- 

 mination in the case of the seeds of N. attenuata. ]\Iore rapid 

 germination of the treated seed is not, however, in general 

 apparent, for at the end of fifteen days in only two instances 

 — 70 per cent for fifteen minutes and 80 per cent for ten minutes 

 — was the germination of the treated seed greater than in the 

 control. The optimum lengths of treatment in this case evidently 

 lie between thirty and sixty minutes for the 50 per cent acid, 

 between ten and fifteen minutes for the 70 per cent, and prob- 

 ably not much beyond ten minutes in the case of the 80 per cent 

 acid. A considerable number of other tests with seed of 78/09 

 of 1911, using both stronger and weaker grades of sulfuric acid 

 for various lengths of time, were carried through. The above 

 table, however, includes the most significant results, though it 

 deals by no means with only those tests in which favorable 

 results after sulfuric acid treatment M'ere obtained. 



Seeds of a number of other Nicotiana species which showed 

 relatively low germination (see page 210) were treated with 

 sulfuric acid in an effort to increase germination and a number 

 of the results are shown in tabulated form below. In each case 

 except the last the seeds were washed after the acid treatment 

 for from forty-five minutes to one hour in running water. 



The prefixes attached to the seed numbers designate the year 

 upon which the seed was gathered. Thus 1906 53/03 refers to 

 seed of 53/03 gathered in 1906 or six years old at the time of 

 making the tests. 



As will be seen in the table below, the effect upon germination 

 of treatment with 70 per cent and 80 per cent sulfuric acid has 

 been investigated in the cavse of old seed of N. Tahacum "Mary- 

 land" and old and new seed of two N. acuminata^Y arieties. The 

 relative amount and rapidity of germination in the old vs. new 

 untreated tobacco seed is taken up at greater length elsewhere 

 (see page 210). In every case in the table below treatment with 

 diluted sulfuric acid has resulted in a rather striking increase 

 in total germination as compared with the controls and also in 

 a rather marked increase in rapidity of germination in the case 

 of the treated seed. 



