194 BOTANICAL GAZETTE [MARCH 
A sample of seeds of O. biennis, taken from a late flowering 
individual, 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 O. suaveolens, the percentage was 
increased from 3 to 14 per cent, for O. muricata from 12 to 80 per 
cent, and for O. Cockerelli, a species which is often very slow in 
germinating, from 2 to 72 per cent. 
It is not improbable that in O. 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. Ina 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 o.1 per cent, 0.05 per cent, and 
0.3 per cent. In cultures of O. Lamarckiana the corresponding 
numbers are for O. nanella 1-2 per cent, for O. semigigas 0.3 per cent 
(Gruppenweise Artbildung. p. 329), while no color mutations have 
been observed as yet. With the origin of O. 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 O. Lamarckiana. 
2. From the cross O. biennis mut. nanellaXO. biennis only 
dwarfs of a uniform type arose (108 Ex). O. biennisXO. biennis 
mut..xanella was in the first generation exactly like pure biennis; 
O. Lamarckiana XO. biennis mut. nanella exactly like O. Lamarckiana 
X biennis. 
O. biennis semigigas is self-sterile, but when pollinated by 
O. biennis gives for one-half pure biennis with 14 chromosomes, and 
for the other half a new, slender type with 15 chromosomes. 
