570 DOUBLED CHROMOSOMES OF OENOTHERA 



3. Besides these main forms, single plants of secondary types 

 were observed. They were one oblonga, two auricula, one candicans, 

 and two hamata. 



4. In almost one-half of the mutants (35 individuals out of 81) 

 the number of chromosomes was 15, or the same as in the older 

 heterogamic mutant races. As a rule, these plants showed all the 

 marks of those races, although, on account of their velutina gametes, 

 they could not be expected to be identical with them. 



5. In the other half of the mutants the chromosome numbers 

 were 16—20, and the external features were correspondingly mixed, 

 but almost always one of the main types could be recognized as the 

 prevailing one. 



6. The 15 chromosome offspring of semigigas belong to different 

 types. Among these some are frequent and others rare. The frequent 

 types are seven in number, and in each of them a different chromo- 

 some must be doubled. Of the rarer ones each must also have one 

 chromosome doubled, but in these cases other factors of the same 

 rod must have been activated. 



7. Among all the mutants, the new form 0. pulla shows the least 

 deviation from the original form 0. Lamarckiana. It is therefore 

 assumed to have its factors located in the central chromosome. 

 The remaining six types are those of the old dimorphic races, each 

 of them designating a lateral chromosome, as had already been 

 deduced by us from other considerations. The rarer types are such 

 as have previously been pointed out as secondary ones. It is assumed 

 that oblonga and auricula have their factors in the scintillans chro- 

 mosome, whereas candicans is derived from cana and hamata probably 

 from spathulata. 



8. In order to get sufficiently sharply distinguished types among 

 the progeny of semigigas, some conditions must be fulfilled. In the 

 first place, velutina pollen should be used for the fertilization, since 

 its qualities, as a rule, are recessive to those of the mutants. Then 

 the culture must be made under favorable conditions, as in the 

 glass covered part of the garden. Also, the young seedlings should 

 be planted singly in small pots, and selected and arranged shortly 

 before being transplanted on the beds. If this is done the mutants 

 belonging to the same type will flower next to one another, thereby 

 giving a striking survey of the uniformity of their main features. 



LITERATURE CITED 

 1. Boedyn, K., Die Chromosomen von Oenothera Lamarckiana mut. simplex. 

 Zeitschr. Ind. Abst. 24:71. 1920. 



