I9I5] 



BAKTLETT—ilASS MUTATION 



445 



f. typica could be identified 

 among them. The reciprocal 

 cross yielded no seeds. 



Inheritance and mutability of 



the characteristic 



mutations 



Of the group of character- 

 istic mutations, including mut. 

 fonnosa, mut. albicans, mut. 

 revoluta, and mut. setacea, only 

 the first is both normally fertile 

 and vigorous. The second is 

 vigorous, but produces few 

 good seeds. The third is 

 almost sterile, and the fourth 

 is not only difficult to cultivate, 

 but like mut. albicans gives 

 very few good seeds. All of 

 the forms were self-pollinated 

 and reciprocally crossed with 

 f. typica in 1914, but, except 

 in the case of mut. formosa, 

 the resulting Fi cultures were 

 xery fragmentary or entire 

 failures. The other three 

 forms bloomed in September, 

 when only a few weak, belated 

 flowers of f. typica were avail- 

 able for the crosses. The 

 results of the cultures are 

 summarized in table VL 



Mut. formos a . — T h e 

 entirely satisfactory cultures of 

 this form show that it is con- 

 stant in the sense that it gives 

 no reversions to f. typica in its progeny. Moreover, there is no 



Fig. 9. — Mul. rcvohila: ;i mature plant, 

 Lexington E-19-21 (for position in pedigree 

 see table II). 



