No. 545] 



NOTES AND LITERATURE 



311 



effects being additive, are responsible for the parental differences, 

 especially when the character in question fluctuates widely as 

 compared with the differences between the several genotypes 

 occurring in F 2 . Thus, suppose three factors, A, B and C, each 

 alike in effect, and each producing the same average increase in 

 length of vegetative period. The F 2 generation of the cross abc 

 X ABC will consist of the genotypes aabbcc, aabbCC, aaBBcc, 

 AAbbcc, aaBBCC, AAbbCC, AABBcc and AABBCC and their 

 crosses. The genotype aabbcc would be similar to the early 

 parent. Genotypes AAbbcc, aaBBcc and aabbCC would con- 

 stitute a group one stage later in flowering. AABBcc, AAbbCC 

 and aaBBCC constitute a third stage, while AABBCC would be 

 equivalent to the late parent. Thus the four stages resulting 

 from these three factors tend to be present in the ratio 1:3:3:1, 

 which ratio is merely one way of stating the properties of an 

 ordinary frequency curve. Earliness being nearly completely 

 dominant, the norm of this curve would be shifted toward the 

 early parent, as Leake found was the case. Even if this progeny 

 were selfed to the tenth generation, by which time heterozygosis 

 would have largely disappeared, the mixture of the four geno- 

 types would still give a monomodal curve. The only exception 

 to this would be cases in which fluctuating variation is not trans- 

 gressive between the genotypes. It is possible that more than 

 three genes were involved in Leake's crosses. 



Crosses between pure lines having no leaf glands and those 

 having leaf glands gave intermediate F r F 2 gave evidence of 

 segregation, but the intermediate and apparently highly fluctu- 

 ating character of the heterozygotes rendered positive conclu- 

 sions difficult or impracticable. 



Complete correlation occurred between flower color and length 

 of petals. White petals were little if any longer than the brac- 

 teoles, while yellow petals were about twice as long. Interme- 

 diates did not occur, and no exceptions were found in over 100,- 

 000 plants. 



Red sap color was independent of the size of the petal but 

 when present it lengthened the vegetative period. This paper is 

 exceedingly clear and lucid in treatment, and we may expect 

 much valuable work from the author in future. 



Dr. Shull has resumed his interesting studies of Bursa.™ He 

 "Dr. G. H. Shull, "Defective Inheritance-Ratios in Bursa Hybrids," 

 yerh. d. Naturforsch. Ver. in Briinn., Bd. XLIX. 



