454 University of California Publications in Botany [Vol. 5 



years was available. In the majority of cases the germination in 

 light and in darkness of nine year old as compared with two year old 

 seed was tested. For 25/06 (tests 15 to 26) the germination under the 

 two conditions of twelve, eleven, nine, seven, six, and two year old seed 

 was investigated. Two year old seed only of five N. rustioa varieties 

 was employed. As will be seen in the table the older seed germinated 

 with a good or fair percentage, although the germination is scattering 

 and the period of maximum germination is later than in the case of 

 younger seed of the same pedigree. 



Various points are brought out in the table above which deserve 

 further investigation. Thus, for example, the poor germination of 

 two year old seed (tests 37 and 38) as compared with nine year old 

 seed (tests 35 and 36) of 78/05 is unusual and may indicate a lessened 

 viability due to continued inbreeding. This matter is especially inter- 

 esting in view of the fact that two year old seed of 78/05 germinated 

 much more heavily in darkness than in light. Again, the heavy 

 germination of the nine year old seed of 71/05 (tests 27 and 29) is 

 worth}^ of notice. 



The notation used in the seventh column of the table to indicate 

 the relation between the germination of seed of the same year in 

 light and in darkness is merely one of convenience and has no particu- 

 lar significance. Thus the " _j_ " sign is employed simply to emphasize 

 the fact that the per cent of germination of the seed in darkness was 

 actually greater than that of the corresponding seed subjected to 

 continuous illumination or under diurnal illumination. In reality 

 practically all those pairs of tests marked "-|-" fall into the " = " 

 section since germination in darkness rarely exceeded germination in 

 light by more than ten seeds. 



There is no doubt that the seed of five representative types of 

 N. Tahanim and of five varieties of N. rustica will germinate readily 

 in darkness. These five varieties of N. Tahacum represent a large 

 proportion of the basic types from which the commercial strains of 

 American tobacco, with which Honing worked, have been derived. 

 Honing {loc. cit., p. 14) found that of twenty-one strains of N. 

 Tahacum received by him under trade names from the United States 

 Department of Agriculture and germinated in darkness more than 

 fifteen germinated only 20 per cent or less and that none of the 

 twenty-one germinated over 50 per cent. I am at a loss to explain 

 this result of Honing or a number of the others which he reports. 

 Since the germinations listed in the above table indicate that germina- 



