432 BOTANICAL GAZETTE ' [December 



large number of zygotes to develop, for the number of ovules in all 

 capsules appears to be about the same. Probably the zygotes 

 which fail to develop into embryos represent the weaker individuals 

 of mut. setacea, or perhaps some stiU more reduced mutation which 

 is incapable of development. The problem, however, must be 

 attacked by cytological methods. It is interesting to observe that 

 the Fj, with an average seed germination of 70 per cent, contained 

 75 per cent of mutations. If aU the seeds had germinated, and 

 the additional plants had all been f . iypica, there would still have 

 been more than 50 per cent of mutations. It seems far more likely, 

 however, that the seeds which did not germinate were either empty 

 or else that they were the weak mut. setacea. 



A comparable degree of mutability to that of Lexington E is 

 known only in the case of 0. Reynoldsii, in which mass mutation 

 was first described. In O. Reynoldsii, also, the great increase in 

 mutability is associated with an enormously increased degree of 

 sterility. The data in regard to the latter species wiU soon be 

 pubHshed elsewhere. 



A number of photographs were made to record the appearance 

 of the mutations at various stages of growth. Figs. 1-5 show a 

 portion of the F2 progeny from Fi parent Lexington E-5, recorded 

 in table II. All of the characteristic mutations are shown, as well 

 as several plants which became the parents of subsequent cultures. 

 Fig. 6 shows 6 rosettes of mut. setacea, one of which will be found in 

 fig. 3. Fig. 7 shows two mature plants of the same mutation, of 

 which one is shown in fig. 5. Fig. 8 shows 4 rosettes of mut. 

 revoluta, 3 of which are likewise shown in figs. 4 and 5. A mature 

 plant is shown in fig. 9. Fig. 10 shows 6 rosettes of mut. albicans, 

 3 of which will be found in figs. 2, 3, and 4. Fig. 11 shows two 

 cauUne plants of the same form. The one on the left is just begin- 

 ning to flower; the one on the right lingered in the rosette condition 

 and would therefore have matured as a stronger plant than its 

 sister. Rosettes of mut. formosa are shown in fig. 12. The main 

 stem of the mature plant is shown in fig. 13, and the identical cross 

 mut. formosaXi. typica in fig. 14. Fig. 15 shows young rosettes 

 of f. typica and mut. gigas. The gigas plant was the particular 

 individual in which E. G. Arzberger determined the chromosome 



