474 BOTANICAL GAZETTE [ JUXE 



triple hybrids are produced— in addition to O. laeta and O. velutina a third type 

 resembling the mother (O. lata or O. scintillans) , but in its special marks inter- 

 mediate between its parents. 



The twin hybrids of O. nanella have been worked out most completely." 

 O. muricata X O. nanella produces the two types laeta and velutina, about 50 

 per cent, of each. The laeta breed true for four generations, but the velutina 

 spht in the F 3 and all succeeding generations, producing velutina and something 

 over 50 per cent, of a form called by DeVries O. murinella, which is a dwarf 

 O. velntina and breeds true. The dwarf character (but not the other O. nanella 

 characters), therefore, reappears in over half of each generation. The discoveries 

 of greatest interest follow. O. velutina X O. murinella gives the same results as 

 O. velutina self-pollinated, i. e., over 50 per cent. O. murinella. From this the 

 conclusion is drawn that the pollen of O. velutina has the same hereditary qualities 

 as that of O. murinella. The reciprocal cross gave 100 per cent. O. murinella 

 (280 plants). The facts are all explained by assuming that the egg cells of O. velu- 

 tina are of hybrid (heterozygote) nature (a X b), while the pollen bears only the 

 dwarf character (a). On self-pollination O. velutina would then give 50 per cent. 

 O. velutina (a X b) and 50 per cent. O. murinella (a) which breed true. This 

 conclusion ,s verified by crosses of O. velutina and O. nanella (since O. velutina 

 X O. nanella gives 57 per cent. O. murinella, and O. nanella X O. velutina gives 

 100 per cent. O. murinella). 



Similarly, O. laeta crossed with O. murinella, O. nanella, or O. velutina gives 



5 ? *? u n l!? eta and 5 ° *** CCnt dvVarfs - Ther efore the egg cells of laeta are 

 also hybrid (heterozygote) in regard to the dwarf character, although when self- 

 poll.nated laeta .breeds true! The pollen of laeta therefore bears the hereditary 

 characters for high stature. This dominates over the hybrid nature of its own 

 egg cells, but is recessive to the egg cells of pure dwarfs. The remarkable situa- 

 tion therefore appears, that the egg cells of both velutina and laeta behave as 



former 



he dwarf character, and the pollen of laeta appears to carry only the character 



tor hurh ctahiro J J 



for high stature. 



behav 



those of other mutants. O. gigas X O. Lamarckiana forms a constant inter- 



mediate race. O. Lamarck 



X O rubnnenns, and O. rubrinervis X O. gigas all give the same hybrid race. 

 u. lata X O gigas, however, gives two types, about half intermediate between 

 O. gigas and O. Lamarckiana, and half intermediate between O. gigas and O. lata. 

 O gigas crossed with O. biennis and O. muricata produces intermediate sterile 



I)eni^ D « V ! IE ^ " UG °' Ueber * Z« illingsbastarde von Oenothera nanella. Ber. 

 Ueutsch. Bot. Gesells. 26a: 667-676. 1908. 



„, !t J Bastarde v °n Oenothera gigas. Ber. Deutsch. Bot. Gesells. 26a: 



754-762. 1908. 



