170 University of California Publications in Botany [Vol. 5 



hybrid corolla diameters formed intermediates in size between 

 the corolla diameters of the parents of the corresponding cross. 

 A suggestion which was advanced with reference to this situation 

 in Fj was that "the occurrence of large flowers, small flowers, 

 and flowers the corolla diameter of which show even,'' degree of 

 gradation betw^een large and small in Fj, of a cross between a 

 large flowered and small flowered variety of X. acuminata, 

 represents the maximum degree of segregation which occurs in 

 such a hybridization." A tentative suggestion as to Fo, also 

 made there, was as follows : ' ' The F2 plants grown from the 

 seed produced by self-fertilizing the flowers of this hybrid may 

 give us a few^ plants bearing flowers the corolla diameters of 

 which show small variation in size. Succeeding generations may 

 reduce the variation still further until we have regained either 

 one or both of the parental varieties which entered into the pro- 

 duction of the Fj generation or have established a new flower 

 size variety which will thereafter come true to a certain diameter 

 of flower which varies only slightly in size. ' ' 



During August, September and October of this year (1912) 

 over five thousand measurements of corolla diameter of flowers 

 on the parental varieties and F^ hj'brids have been made. The 

 results of these measurements make plain the necessity of ob- 

 serving the behavior of F, individuals before these F2 results 

 can be accurately commented upon. In addition it seems desir- 

 able to obtain measurements upon the flowers of the following 

 types of N. acuminata plants in 1913 (1) the F^ hybrids of 1910 

 grown in the field again and also under various controlled experi- 

 mental conditions; (2) the F^ hybrid remade in 1912 and grown 

 under the conditions stated in (1) ; (3) the parental varieties 

 to be produced from 1909, 1910, and 1911 seed and gtown under 

 these vsame conditions; (4) F2 generation plants brought to 

 maturity in the greenhouse; and (5) the obtaining of hybrid 

 seed in the greenhouse from the parental varieties therein grown 

 and the production from such seed of F^ plants some of which 

 will be grown in the field and some in the greenhouse. The value 

 of certain of these desiderata was not appreciated at the start of 

 the growing season just past and in the other cases lack of room 

 and other facilities made their satisfaction impossible. The data 



