t 



t 



I 



( 



f 



V 



\ 



1907] GATES—HYBRIDIZATION OF OENOTHERA MUTANTS 9 



The possibilities of apogamy in other mutants are apparently not 

 so good, and such a condition seems rather unlikely, especially in O. 

 nanella, where some of the hybridization results practically exclude 

 the possibility of apogamy in these cases. Thus, O. nanella 9x0. 

 biennis $ gave (DeVries /. c. 2 1476) in two crosses 554 plants, none of 

 I which were O. nanella; while the reciprocal cross gave 96-100 per 



cent. O. nanella among 356 plants. Hence in both cases the pollen 



was 



amous embryos, at least of any kind known 



formed 



THE NUMBERS OF CHROMOSOMES 



F 



In my earHer paper^ it was shown that the sporophyte number of 

 chromosomes in O. lata is fourteen, while in the O. Lamarckiana 

 plants appearing in the first hybrid generation from a cross with O. 

 lata^'^ the number is at least twenty. It was assumed therefore that 

 the pure O. Lamarckiana parent had at least twenty chromosomes as 



the pure O 



number. Examination 



number is fourteen. This 



remarkable 



trated thus : 



O. lata O Limarckiana 



14 20 or 21 



O, lata O. Lamarckiana 



Fig. 3 



plants, whose erametophyte number 



J 



when crossed give rise in the first hybrid generation to the two parent 

 fonns, one of which has fourteen chromosomes as the sporophyte 

 number, while the other has twenty or twenty-one. 



In O. lata the count of chromosomes was made in the pollen 



found to be fourteen. It has since been made in 

 sstips of thp flower, and is found to be constantly 



mother cells and 



somatic 



shall refer to the O. Lamarckiana 



pollinated by O. Lamarckiana as "the Lamarckiana hybrid. 



