;!IS Lutz, Triploid Mutants in Oenothera. 



All individuals which I have observed having a chromosome 

 number much in excess of that of (). Lanxnr.kiana displayed certain 

 characters strongly suggesting those of 0. gigas, chiefly noted in 

 the stoutness of all parts. This was true of both mutants and 

 hybrids, and the only exceptions noted were those of certain second 

 generation hybrids to be later described which maintained a high 

 chromosome number in spite of their weak and sickly appearance. 

 Even these retained the large buds and flowers of 0. gigas. We 

 may therefore assume that the possession of g/yas-like vegetative 

 characters by any form is an indication (not a proof) of a chro- 

 mosome number considerably in excess of that of 0. Lamarckiana**). 



On the basis of this assumption it would appear that 80 or 

 more of the above described 98 offspring of the 21 -chromosome 

 mutants had a somatic chromosome number of 14, or in the region 

 of!4(/to, albida and the 5509 type), but that most of the remainder 

 approached or equalled that of the parents, or of 0. gigas. 



This is indeed very suggestive of irregularities in the divisions 

 of the germ cells of the 21-chromosome mutants. In this connection 

 the report of Geerts (16) upon the reduction division of the germ 

 cells of a 21 -chromosome offspring of 0. fata X () - gigas is of especial 

 interest: 



,,In unseren Oeo#/zera-Bastarden treten die Chromosomen aus 

 dem Kniiuel in der vegetativen Zahl hervor, also 21 (Fig. 1). Nach 

 der Auflosung der Kernmembran zeigen sie den Anfang der paar- 

 weisen Anordnung, aber es entstehen nur 7 Paare, wahrend 7 Chro- 

 mosomen ungepaart bleiben. Bei der ersten Teilung, bei der Re- 

 duktionsteilung, trennen sich von den 7 Chromosomenpaaren ganze 

 Chromosomen voneinander, welche zu je einem Pol gehen (Fig. 2). 



14) Jt should be stated in the connection that mutants with low chromosome 

 numbers have been found with relatively stout stems and thick buds, so that the 

 increased stoutness of certain parts is not an invariable indication of increased chro- 

 mosome number. This condition, however, was confined to forms of low stature, 

 and to individuals which resembled 0. gigas in no other particular. 



Gates (13), in discussing the offspring of 0. lata X 0. gigas, mentions the 

 possibility of an individual having the tetraploid number of chromosomes owing its 

 gigas characters to the number of chromosomes rather than their source. He also 

 brought out evidence to show, form a series of measurements, that certain cells of 

 the tetraploid mutant 0. gigas are conspicuously larger than those of O. Lamarck- 

 iana having the diploid number, and states that the larger cells doubtless account 

 for the greater stature of this plant (12). 



While I think it is probable that the increased stoutness of 0. gigas, and 

 perhaps certain other characters as well, are the direct result of the doubling of 

 chromosome number and increase in cell dimensions, I believe, as Stomps has 

 stated (21, p. G3), that it is very improbable that all of the characters of this 

 mutant are the direct expression of this increase. It is certain that the larger cells 

 of (). gigas are not responsible for increased height in this plant, for the height 

 is not increased. As previously stated, dc Vries described 0. gigas as attaining 

 about the same height as that of 0, LamarcMana. 



