i9 1 7] DEVRIES— OENOTHERA 19 



purely pollinated capsules of 4 specimens of my culture of 191 5, 

 which was the fourth generation of my race. I took them carefully 

 out of the fruits, mixed those of 5 successive capsules of the same 

 spike, and counted 200 grains from each lot. I soaked them in 

 water, pushed this into their seed coats by means of a pressure of 

 8 atmospheres for about 24 hours, and afterward laid them out to 

 germinate in small glass tubes in a stove at i< 



C. rr Within 



the larger part of the seeds germinated, giving percentages of 

 85, 84, 73, and 70 for the 4 lots. I then opened the remaining 

 grains and found fully developed germs in almost all of them. 

 The percentage of germs, being the sum of the two trials, came to 

 99, 96, 96, and 93, and there is no doubt that if they had been left 

 in the stove for a longer time, almost all of the resting germs would 

 have shown signs of germination. 



The proportion of rapidly germinating grains and that of empty 

 ones depend in a high measure upon the external conditions of life. 

 During the summer of 19 14 I cultivated 2 lots of individuals from 

 seeds of the same parent plant, giving to one of them the ordinary 

 favorable conditions of my garden, and keeping the others in a dry 

 soil without manure. The seeds of the 2 most vigorous specimens 

 of both lots, taken from self-fertilized capsules, were tried. They 

 contained 99 and 99 per cent of germs for one group, but only 72.5 



and 7*. c ner cent for the. other oroun. The 



same 



the amount of grains which germinated within the first 

 ie figures were 80-88 per cent in one case and 53 per cer 



other 



case. 



12 



hereditary property of producing about 



mutation 



the visible changes in the external structure. The same 

 accompanies the mutation into gigas, rubrinervis, and some n 



lata 



0. scintillans, 0. cana* and 



J method has been followed in all the experiments to be described in the text. 

 It is described in the following papers; The coefficient of mutation in Oenothera 



biennis L. 



kiinstliche Beschleunigung 



Wasseraufnahme in Samen durch Druck. Biol. Centralbl. 35:161-176. 19*5- 



"Biol. Centralbl. 35:174-175, where 0. blandina was provisionally indicated as 

 mut. nov. B. 



