Lutz, Triploid Mutants in Oenotliera. \\'\ 



invariably have the same somatic chromosome numbers, it is prob- 

 able that somatic chromosome number in 0. lata is constant. 



From the fact that an offspring of 0. lata corresponding to 

 the type of that described by Gates for the "'mosaic' hybrid" (7) 

 has never been reported except as the offspring of 0. lata X 0. 

 Lamarckiana and 0. lata self-pollinated, it seems probable that this 

 plant also originated as first stated, or as the offspring of 0. lata 

 pollinated by 0. lata. However, it is possible that it may have 

 resulted from the fertilization of 0. lata by some other form cap- 

 able (in union with 0. lata) of producing this type. 



The evidence is less clear for the remaining 8 of the 10 

 individuals first termed " 0. Lamarckiana hybrid". Since this group 

 of 10 was first described as conforming more or less completely 

 to the characters of the pollen parent, 0. Lamarckiana, they must, 

 according to a well known mathematical rule, have resembled each 

 other more or less. If, as stated in the next paper (8), the pure 

 0. Lamarckiana and the 0. Lamarckiana hybrid were 'identical in 

 external appearance' then there can be no question but that these 

 ^Lamarckiana hybrids" were, with respect to each other, 'identical 

 in external appearance'. In either case, since one of the 10 had 

 20 chromosomes, and possibly another of this lot, 21, it would 

 seem probable that the remaining 8 or 9 had similar numbers and 

 were likewise derived from seeds of the 'unguarded seed-package'. 

 However, if I understand Dr. Gates' statements correctly, at least 

 one of the original '''Lamarckiana hybrids" (and probably two) was 

 later included in a group of hybrids described as having 'almost 

 or quite the identical appearance of 0. gigas' (10), and still later 

 was mentioned in a group of hybrids which 'appeared to have been 

 intermediate between 0. lata and 0. gigas' (13). We have, therefore, 

 no definite basis for speculation concerning the probable origin of 

 these 10 plants. 



While it is not probable that any of Gates' original 10 u La- 

 marckiana hybrids" (7) had the same vegetative characters as those 

 of the "'mosaic' hybrid", it is quite as possible that one or two 

 of the 21-chromosome plants of unknown male parentage were 

 triploid mutants, as that they were hybrid offspring of 0. lata X 

 0. gigas. 



To review briefly, a single type of 21-chromosome mutant, 

 represented by 8 individuals, appeared among six separate cultures 

 of Oenotheras at the Station for Experimental Evolution. It is possible 



that the "'mosaic' hybrid" of Gates' culture also belonged to 

 this group. 



A second mutant, represented by a single individual, of a type 

 of vegetative character in some respects quite distinct from the 

 XXXII. 27 



