106 University of California Publications in Botany [Vol. 5 



YII. DISCUSSION OF INHERITANCE OF CHARACTERS 

 ACCORDING TO WEIGHT OF SEED 



1. Shape, Size and Weight of Parental Seed of 1906 and 1907. 



The seed which was used to reproduce .Y. Tahacum var. 

 macropJiylla and X. Tahacum var. virginica in 1907 and 1908 

 was examined under the lens and also weighed. There was 

 under the reading-lens a greater uniformity in shape and size 

 of the seed of both parents than that which has above been 

 noted in reference to the shape and size of the F^ hybrid seed 

 produced by the cross between these plants. The average length 

 and breadth and the length-breadth index of the seed .V. Tah- 

 acum var. virginica and the seed of .V. Tahacum var. m,acrophylla 

 harvested in 1907 is given in the following table. 



A'. Tahacum var. virginica N. Tahacum var. macrophyUa 



Length Breadth Length- Length Breadth Length- 



breadth index breadth index 



0.76 mm. 0.55 mm. 72.48 0.88 mm. 0.61 mm. 69.31 



The average weight of 200 seeds of N. Tahacum var. virginica har- 

 vested in 1906 was only 0.0001 gr. less than the average weight of 200 

 N. Tahacum var. virginica harvested in 1907. 



400 N. Tahacum var. virginica seed harvested in 1906 and 1907 weighed 

 (average for 100 seeds), 0.0069. 



200 N. Tahacum var. macrophylla seed harvested in 1907 weighed (aver- 

 age for 100 seeds), 0.0078. 



These 600 parental seeds were weighed just as before de- 

 scribed in connection with the weighing of the F^ generation 

 hybrid seed. In picking out the seed to be weighed, no effort 

 was made to make any distinction between seeds of slightly dif- 

 ferent sizes and shapes — i.e., the average run of seed was taken 

 except that the small number of ill-formed, chaffy seed that 

 occurred was not included. 



