282 PLANT HYBRIDIZATION BEFORE MENDEL 



according to the ratio 1:2:1 {Triticum spelta, vulgar e and 

 compactum all have 42 chromosomes as the diploid number). 



Dicoccum-vulgare crosses by the same investigator gave likewise 

 a 1 : 2 : 1 ratio for inheritance of length of spike, dicoccum hav- 

 ing 28 chromosomes as the diploid number. 



The fact that results for awn-inheritance are, Fj^ awnless ; F2 

 awnless-awned, 3 : 1, was first determined by Biffen (1905), and 

 has since been repeatedly confirmed by the work of some fourteen 

 investigators. 



The dominance of pubescence over glabrousness in the glumes 

 was also first determined by Biffen in 1905, in vulgar e crosses. 

 Results for similar inheritance in other Triticum crosses has like- 

 wise been determined. Exact investigations in inheritance of brown 

 glume color were first carried out by Nilsson-Ehle in 1909, the 

 Fo ratio being found for the most part to be 3 : 1 but sometimes 

 15 : 1. Similarly Love and Craig (1919) found a 15 : 1 ratio 

 between a brown vulgare and a yellow durum^ thus indicating the 

 presence of two genes for brown glume color. 



This will suffice for a brief review of the present genetic status 

 of the characters investigated by Spillman. 



The writer concludes, as a result of his investigation : 



"while the results here reported are not sufficient to justify the posi- 

 tive assertion that certain quantitative laws govern the transmission of 

 parental characters to hybrid offspring, yet they point so strongly in this 

 direction, that we may state some of these laws provisionally, looking to 

 future investigation for their confirmation, modification, or rejection." 

 (P- 93-) 



These provisional laws are stated as follows : 



"That similarly bred hybrids tend to be alike in the first generation, 

 and to be intermediate between the parent forms, and that rarely an in- 

 dividual resembles one parent more or less closely, has been stated by 

 others. We may add to this, provisionally at least, the following : 



.(1) "In the second generation of hybrids of similar breeding (with 

 close fertilization), the same types tend to occur and in definite propor- 

 tions ; 2 of these types are like the parents, the others include all possible 

 intermediate forms. 



(2) "with few exceptions, the most abundant type in the second gen- 

 eration is the same as the type found in the first generation, whether the 

 first generation was strictly intermediate between the parents or not." 

 (P- 93-) 



It is a matter of some interest to record such a succinct and 

 definitely scientific attempt at a statement of the conditions gov- 



