Xonchromosomal Inheritance 541 



has can be traced back through plastid division to the plastids 

 that were present in the embryo sacs. Therefore, the factor 

 that determines the plastid condition of a plant is the situation 

 in the embryo sac, which in turn is a matter of the plastid situ- 

 ation in the particular part of the plant that gave rise to that 

 embryo sac. Thus, in ^lirabilis, the inheritance of chlorophyll 

 is purely a maternal matter. 



An interesting plastid behavior has been reported in Oenothera, 

 by Renner, who also first suggested the presence of complexes 

 in that genus. If Oe. Lamarckiana is crossed with the California 

 species, Oe, Hookeri, two types of hybrids are produced, Hookeri- 

 laeta, which has the complexes ^hookeri and gaudens, and Hook- 

 eri- velutina, with the complexes ^hookeri and velans. If Hookeri 

 enters ttfe cross as the female parent, both types of hybrid off- 

 spring are normally green. When, however, Lamarckiana is the 

 female parent, the velutina hybrids are pale yellow and usually 

 die at a very early stage, although the laeta hybrids are normal 

 in color. It has been assumed by way of explanation that the 

 two species have different kinds of plastids, a not impossible sup- 

 position when one considers the long period of complete isola- 

 tion under which they developed. The further assumption is 

 made that Lamarckiana plastids are not able to survive when 

 the genetic constitution of the plant is made up of the velans 

 and ^hookeri complexes. A peculiar feature of Oenothera is that 

 a few chloroplasts enter the zygote through the pollen tube, al- 

 though far more are normally introduced through the embryo 

 sac. When Oe. Hookeri is the female, some Lamarckiana plas- 

 tids enter the zygote from the pollen tube but a great many more 

 Hookeri plastids are introduced through the female side. In the 

 velutina hybrids, probably the Lamarckiana plastids disintegrate, 

 for these hybrids usually had a few yellowish spots although as 

 a whole the plant was green. Supposedly these yellowish spots 

 have chloroplasts which came from the male parent and de- 

 generated. In like manner, in the velutina hybrids from the 

 reciprocal cross, some of the plants had green spots although 

 most of the plant was yellowish. The green spots are believed 

 to be from Hookeri chloroplasts that entered the zygote through 

 the pollen tube and survived, whereas the Lamarckiana plastids 

 that came from the embryo sac, and, therefore, were far more 

 numerous, degenerated. 



