OENOTHERA LAMARCKIANA MUT. VELUTINA. 171 



exactly corresponded to 0. blandina itself; in comparing it from 

 its first youth up to the tine of flowering and fruiting, I could not 

 discover any difference. This one should be considered as the velutina, 

 therefore, and will be called 0. (Lamarckiana x blandina) velutina 

 a.s.o. The other type was evidently a laeta. During some stages of 

 its evolution it was almost wholly like 0. Lamarckiana, but later 

 it changed its appearance and displayed some of the characters 

 which usually distinguish the different forms of the hybrid laeta 

 from their parents. For this reason I shall call it 0. (Lamarkiana x 

 blandina) laeta, or briefly 0. blandina laeta, implying by this name 

 only the presence of one or more characteristics of the laeta type, 

 but not necessarily all of them. 



According to the species which determine the splitting in 0. 

 Lamarckiana, the types of hybrid laeta may be divided into two 

 groups. One of them is small-flowered and ordinarily tall, corre- 

 sponding to the rigida type described and figured in my book (pp. 

 73, 80, 81). To this type appertain the laeta produced by 0. biennis, 

 0. muricata, 0. Cockerelli, and 0. biennis Chicago. The other type 

 has large flowers; it embraces only the 0. (Hookeri x Lamarckiana) 

 laeta and its reciprocal. The flowers have the same size in both 

 parents, and therefore this size is not changed in the hybrids. In 

 the cross of 0. Lamarckiana and blandina the same rule prevails, 

 the flowers of the hybrid being not rarely even somewhat stouter 

 than those of the parents. 



0. blandina laeta shows the greatest affinity to 0. Hookeri laeta, 

 not only in the flowers, but also in other respects, as, for example, 

 in the stature at the time of flowering, which in both hybrids comes 

 much nearer to that of 0. Lamarckiana than any of the small- 

 flowered hybrid laeta. Far more interesting, however, is the simi- 

 larity in its behavoir in the second generation, after self-fertilization. 

 The Hookeri laeta are the only laeta as yet known to split; all laeta 

 of other extraction and all the velutina as yet studied give a uniform 

 progeny. But the Hookeri laeta split in every generation into laeta 

 and velutina which are exactly like the original twins 1 ). The same 

 phenomenon is seen in 0. blandina laeta, although as yet I have 

 only cultivated one second generation from one cross. This was 

 0. blandina x 0. Lamarckiana, made in 1913. The first generation 

 in 1914 gave 59 per cent velutina and 41 per cent laeta, and the 

 progeny of the latter split into the same two types in 1915, giving 



x ) See the pedigrees in Gruppenweise Artbildung, p. 131. 



