FACTORS INFLUENCING FLOWER SIZE IN NICOTIANA 
WITH SPECIAL REFERENCE TO QUESTIONS OF 
INHERITANCE! 
T. H. GooDSPEED AND R. E. Clausen 
L Introduction 
During the past five years the inheritance of flower size has been 
of interest in connection with the study of hybrids made in the Uni- 
versity of CaHfornia Botanical Garden between various pure Hues 
of Nicotiana species and varieties. Three flower size varieties of N. 
acuminata (Graham) Hook. (Setchell, 191 2, p. 23) were crossed back 
and forth and the hybrids examined up to and including F3 (cf. 
Goodspeed, 191 2 and 191 3, (i)); species hybrids between N. sylvestris 
Speg. & Comes (Setchell, loc. cit., p. 29) and a number of N. Tahacum 
L. varieties (ibid., pp. 3-1 1) have also been under observation and 
their Fi flower size and the size of the flowers in the case of crosses 
of the parents back onto the hybrids have been studied in detail. At 
the present time a study is being made of the flower size of a self-fertile 
hybrid between N. Langsdorfii Weinm. and N. Langsdorfii var. 
grandiflora Comes (Setchell, 1912, p. 15) which should be of interest 
because of the marked difference in flower size of the parental types. 
In the collection of some 25,000 measurements on the length of 
corolla tube and the spread of corolla limb of flowers on the various 
hybrids above noted certain very definite difficulties have been en- 
countered. These difficulties have had their influence as well in 
determining the technique of taking the measurements as in directly 
influencing the value and interpretation of the general results obtained. 
East (1913, pp. 177 and 178) finds reason to believe that corolla size, 
which he recognizes as a ''character complex," is "comparatively 
•constant under all conditions attending development." In this con- 
nection he refers to the well-known fact that other size characters, in 
contrast to this comparative stability of corolla size, are subject to a 
^ The experiments herein reported upon were assisted by that portion of the 
grants to the University of California, College of Agriculture, under the Adams Fund, 
which was put at the disposal of Prof. W. A. Setchell. 
332 
