24 THE COEFFICIENT OF MUTATION IN OENOTHERA BIENNIS L. 



with an undeveloped germ. From these figures we see that the 

 production of seedlings from a sample of seeds may be more than 

 doubled by the pumping method, while all or almost all the healthy 

 germs may be made to germinate. Numerous similar instances 

 could be added. 



A sample of seeds of 0. biennis, taken from a late flowering indi- 

 vidual, produced only 2 per cent of seedlings in the first two days, 

 while a control sample, after having been exposed in water to a 

 pressure of 6 atmospheres, produced at once 80 per cent of seedlings. 

 In the same way for 0. suaveolens, the percentage was increased 

 from 3 to 14 per cent, for 0. muricata from 12 to 80 per cent, and 

 for 0. Cockerelli, a species which is often very slow in germinating, 

 from 2 to 72 per cent. 



It is not improbable that in 0. Lamarckiana the hard seeds 

 may contain more mutants than the easily germinating ones, which 

 have thus far been studied. It seems even possible that they may 

 conceal some new, as yet unobserved, types of mutations. The 

 new method enables us to bring almost all the germs to germination, 

 as well as to separate the seedlings of the different groups. 



Before concluding, I may be allowed to recommend this method 

 for the study of various other kinds of seeds also. 



Summary. 



1. In a culture of 8500 specimens of pure line Oenothera biennis 

 L. 8 mut. nanella, 4 mut. semigigas and 27 mut. sulfurea arose, 

 giving the percentages of about 0.1 per cent, 0.05 per cent and 

 0.3 per cent. In cultures of 0. Lamarckiana the corresponding 

 numbers are for 0. nanella 1-2 per cent, for 0. semigigas 0.3 per cent 

 (Gruppenweise Artbildung, p. 329), while no color mutations have 

 been observed as yet. With the origin of 0. Lamarckiana. the 

 mutability for dwarfs, therefore, must have increased at least tenfold, 

 and for gigas types about sixfold. The material cause for this 

 improvement is in all probability the same as or closely connected 

 with the cause of the largely increased number of mutative forms 

 which are known to start from 0. Lamarckiana. 



2. From the cross 0. biennis mut. nanellaxO. biennis only dwarfs 

 of a uniform type arose (108 Ex). 0. biennis xO. biennis mut. 

 nanella was in the first generation exactly like pure biennis; 0. 

 Lamarckiana xO. biennis mut. nanella exactly like 0. Lamarckiana 

 x biennis. 



0. biennis semigigas is self-sterile, but when pollinated by 



