OENOTHERA MUTANTS WITH DIMINUTIVE 
CHROMOSOMES! 
Anne M. Lutz 
A. Introduction 
For a number of years the writer has devoted considerable attention 
to the study of the somatic chromosomes of Oenothera Lamarckiana 
and its derivatives in an effort to ascertain whether or not each species 
or type is represented by a definite, fixed number of chromosomes. 
Having found and announced (Lutz, '12) that all forms having iden- 
tical somatic characters throughout all stages of their development 
invariably have the same number of chromosomes, we may now con- 
sider some of the results of these studies in detail. This report may 
be considered the first of a series of three dealing with somatic chrom- 
osome number in mutants of the Lamarckiana group of Oenothera.^ 
During the first four years investigations were conducted at the 
Station for Experimental Evolution,^ Cold Spring Harbor, where 
careful work on an extensive scale was made possible by the kindness 
and generosity of the director. Professor Charles B. Davenport. 
Owing to the nature of the study, a thorough knowledge of the 
somatic characters of each individual became, clearly, a matter of 
first importance; therefore, from the time of the appearance of the 
seedling leaves until the end of the fruiting period late in October, 
attention was directed almost exclusively to the careful study of the 
somatic characters of the growing plants. 
Tips of rapidly growing roots from rosettes in 3-inch pots, sup- 
plemented by various somatic tissues of young buds, were employed 
for the determination of somatic chromosome number."* All, with the 
^ Reported in a paper read before the Botanical Society of America, December 29, 
1915- 
" To be published in this Journal. 
3 Maintained by the Carnegie Institution of Washington until March, 191 1. 
^ For the sake of brevity, the rather awkward term of " chromosome number " 
will be substituted frequently for " number of chromosomes " throughout this 
report and others to follow. 
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