Lutz, Triploid Mutants in Oenothera. 



the LaniaiTh-i<iini parents of 5 of the 6 1910 triploid mutants 11 ) 

 and operations upon these two groups were conducted by separate 

 individuals. That 0. gigas pollen should have accidentally reached 

 the guarded stigmas of the 3 Lamarcldana parents of these mutants 

 is therefore not probable. The fata parent of the 6th plant was, 

 however, grown near the g if/as cultures. 



In 1910 a mutant of a type of character in some respects 

 quite distinct from that of the form just described was observed 

 in still another culture (6052) of 0. Lamarckiana X 0. Lautarckiami. 

 As in the case of the 1910 21 -chromosome mutants derived from 

 the fertilization of (). Lamarckiana by 0. Lamarckiana, 0, yiyas 

 was grown a quarter of a mile distant from the Lamarckiana pa- 

 rents of the mutant in question, and operations upon the two groups 

 were conducted by separate individuals, so it is here also improbable 

 that the plant in question was derived from the accidental fertilization 

 of the female parent with 0. gi'gcts pollen. The chromosome numbers 

 of the parents were not determined; they were typical Lamarckianas, 

 however, and it is therefore probable that the somatic chromosome 

 number of each was 14. 



In the greenhouse rosette stage, this plant, which I shall 

 designate by its pedigree number 5589, was first described as being 

 similar to 0. Lamarcldana, though the center of the rosette appeared 

 a little more compact, and the leaves were broader and more grayish 



11) Although the actual number of chromosomes was determined in but 3 of 

 the 8 mutants above referred to, the term "21 -chromosome mutant'' is here used 

 merely as a temporary designation for all plants "having the same vegetative charac- 

 ters as the 3 individuals which were found to have 21 chromosomes. Following 

 papers will show that, so far as has been observed, all individuals which have the 

 same vegetative characters throughout their life histories invariably have the same 

 chromosome numbers. The exceedingly rare occurrence of a cell with a chromosome 

 number varying from the normal by one, or having double that of the type and two 

 tips which showed certain irregularities that will be later described, - - were practically 

 the only exceptions noted in a total of 9441 tips and 18G buds studied. While it is a 

 very common experience to find two plants with identical chromosome numbers 

 differing conspicuously in their vegetative characters, I have never observed a single 

 instance of two plants having the same vegetative characters in all stages of devel- 

 opment, differing in chromosome number. Mention was made in one of my first 

 reports (19) of several examples of supposed variation of chromosome number among 

 individuals of certain species, but it will be shown in following reports that these 

 supposed variants were demonstrated by later cultures to have been distinct forms. 



The above assertions are based upon 5 years study of somatic chromosome 

 number in the Oenotheras, 4 of which were in relation to vegetative character. 

 Somatic chromosome number has been studied in 300 individuals (all but 8 of which 

 were of known parentage and from guarded fertilizations) and exactly determined 

 in 228 of this lot. All but 14 of the 300 were descended from seeds or plants from 

 de Vries' and were grown at the Station for Experimental Evolution. 2 of the 

 remainder were grown by Professor de Vries', and the remaining 12 by Dr. D. T. 

 MacDougal at the New York Botanical Garden. The latter were derived from 

 cultures of English ancestry. 



