1913] Goodspeed: Nicotiana Hybrids 171 



that may be accumulated from the above outlined material to- 

 gether with that which is at present available should go as far as 

 it is possible to go toward settling the significance of fluctuating 

 variability in the experimental results thus far obtained and in 

 those that it is hoped may be obtained in succeeding hybrid 

 generations (cf. also, Shull, 1902 and 1904, Tower, 1902 and 

 1906 and Love, 1910 and 1911). The importance of this factor 

 has been better appreciated this year (1912) during which the 

 parental varieties have been grown in a different situation and 

 have exhibited considerable increase in individual flower size and 

 a slightly increased fluctuating variability. The present paper 

 is thus presented merely as a preliminary report which it is hoped 

 will give a hint as to the various lines along which the problem 

 involved is to be approached and also serve as the vehicle for the 

 presenting of certain views concerning a problem of somewhat 

 larger significance. 



As will be seen by reference to an earlier paper {loc. ciL), 

 during the seasons 1910, 1911 the measurement of flowers on 

 varieties I, II and III showed that their mean corolla diameters 

 were respectively 27, 20 and 13 mm. with fluctuations never 

 exceeding two millimeters either greater or smaller than the 

 mean diameter in each case. Thus variety I bore flowers having 

 corollas with diameters from 25 to 27 mm., variety II bore flowers 

 having corollas with diameters from 19 to 22 mm. and variety 

 III flowers having corollas with diameters from 13 to 15 mm. 

 The measurements in 1912 give the following results : Variety 

 III varied in corolla diameter from 15 to 18 mm., with the mean 

 diameter approximately 16 mm., Variety II showed fluctuations 

 between 22 and 26 mm., with the mean diameter approximately 

 24 mm., and Variety I bore flowers the corolla diameters of which 

 showed extremes of fluctuation at 30 mm. and 35 mm. with the 

 mean diameter approximately 32 mm. The size of the flower has 

 thus been increased throughout and the fluctuation in coroUa 

 diameter also increased as compared with the results of the pre- 

 vious two years measurements. The plants, parent and hybrid, 

 of N. acuminata were grown on higher, better drained, less de- 

 vitalized land and obtained a maximum of sunlight and heat 

 (cf. Goodspeed, loc. cit. p. 123). The plants were spaced in the 



