246 University of California Puhlications in Botany [Vol. 5 



extent of really significant germination is approximately the same. 

 78/05 represents the parent of the hybrid H 8. A corresponding 

 situation holds for the seed of the F^ .V. rustica hybrids. Thus 

 H 47 and F^ H 47 P20 and P^ correspond in their manner of germi- 

 nation to 17/07, which was the female parent in the cross. Simi- 

 larly. H 46 and F^ H 46 P,„ show the extended period of germination 

 which is characteristic of 16/07, the female parent of the cross. F^ 

 H 46 P-. on the other hand, compares more closely in its germination 

 with 17/07, H 47 and F, IT 47 P., and P.. F^ H 46 P, and F^ H 47 

 Poo shoAV a relatively high percentage of total germination, while F^ 

 H 46 Po„ and F^ H 47 P^ show a relatively low percentage. 



Tables IV and V exhibit the germination of 30/06 and 22/07 and 

 the seed of Fo and F.j of hybrids made between them. H 23 represents 

 the cross 30/06 X 22/07, and H 24 its reciprocal. The seed resulting 

 from the cross-pollinations and the seed from Fj plants were not avail- 

 able. As seen in Table I and Table IV, the seed of 30/06 has a 

 characteristically extended period throughout which germination con- 

 tinues to take place. This fact may have led to the statement made 

 by Setchell (1912, p. 8) concerning the "poor germinating power" 

 of this X. Tahacum variety. If under the most favorable conditions 

 significant amounts of germination are taking place only after nearly 

 three weeks in the germinating case, the viability of such seed sown 

 in soil would have appeared to be low, especially as most of the other 

 N. Tahacum varieties complete their germination in less than two 

 weeks. 



The F, and F^ seed of H 23 and H 24 are rather distinctly differen- 

 tiated among themselves in a number of ways. It is characteristic of 

 the parent 22/07 to have a limited duration of significant germination 

 (cf. Goodspeed, I.e., p. 210), which is in contrast to the extended period 

 of germination characteristic of the other parent, 30/06 (Table I). 

 Thus the day upon which maximum germination takes place occurs 

 in the case of 22/07 relatively early in the test, while in the case of 

 30/06 it occurs relatively late. The seed of F, II 23 F., P„,, F, H 23 

 P31 Poo, and Fo H 24 P^ Po in a general way parallels 30/06 in these 

 respects, while the seed of F, H 23 Po^ Po^, F3 H 24 P.,, P.,;. P^, and 

 F3 H 24 Pi3 P04 Pi corresponds more nearly to 22/07. Similarly the 

 seed of Fg H 24 P34 P03 occupies roughly an intermediate position be- 

 tween 22/07 and 30/06, while within the germinating period of three 

 weeks the seed of F, H 24 Pg Po and Fo H 24 Pg^ P^o germinated only 

 25 per cent and 33 per cent respectively and the period during which 



