19 1 7] DeVRIES— OENOTHERA 5 



on a length of half a meter in the middle part of the spike, at the end 

 of September, and found 30 of them on 0. blandina, but 75 on O. 

 Lamarckiana, both on very vigorous annual specimens. From 

 this the internodes of the spike are 1 . 7 against o . 7 cm., or more than 

 twice as long as those of the parent species. The average numbers 

 of flowers which open on a spike during an evening are inversely 

 proportional to these figures. For many crosses I have castrated 

 five successive flower buds of 0. Lamarckiana on one day and 

 pollinated them the next day, whereas the crossing of 5 flowers on 

 a spike of O. blandina usually lasts 4 or more days, which makes 

 quite a difference in the technical work. 



Of course, there are a number of distinguishing points of less 

 value, but their description would remain vague unless strict 

 averages could be given; and since all characters are more or less 

 dependent upon the conditions of soil and culture, it is doubtful 

 whether even averages would be reliable. I shall return to this 

 point in the description of the hybrids. 



In comparing this description with that given in my book on 

 Gruppenweise Artbildung for O. (Lamar ckianaXO. biennis Chicago) 

 velutina, it will easily be seen that the two belong to the same type. 

 In the garden, when groups of 10-30 plants are compared, this 

 similarity is of course far more striking. It is at once clear that 

 O. blandina must be a true and pure velutina. 



If we now try to resume this description in such terms as to 

 distinguish a number of probable units, the combination of which 

 might constitute the type of velutina, I might propose the following: 

 (1) slender stature; (2) long internodes of the flower spike; (3) 

 leaves narrow, folded longitudinally and smooth, that is, without 

 bubbles; (4) flowers cup-shaped; (5) hairiness of all organs; 

 (6) abundance of red color in the younger parts. It is obvious, 

 however, that some of these points may go together and depend 

 upon one unit, but on the other hand it must be conceded that this 

 list may be far from complete. Most of these assumed units are 

 recessive to the corresponding qualities of O. Lamarckiana, but 

 the smoothness is dominant over the bubbles, which are evidently 

 due to a lack of growth parallel to the surface of the blade of the 

 leaf. This enables us to separate smoothness from the larger part 



