142 University of California Puhlications in Botany [Vol. 5 



between 27 mm. and 17 mm. and III$X II J* between 22 and 

 14 mm. The relative degrees of fluctuation in corolla diameter 

 are well brought out in plate 32. All the drawings with the 

 exception of that marked 11$ X HIJ* were made from fresh 

 material, suitably selected to show the extremes of variation 

 among parent and hybrid plants. It must be emphasized that 

 these extremes of variation were continually observed on single 

 plants of the various groups of hybrids and did not occur simply 

 as isolated instances in the measurements of an entire group. 

 Thus, corolla diameters in plant 2 of III 5 X I d^ vary as follows 

 between October 2 and November 20. The daily average is also 

 given. 



Date 1911 Get. 2 4 6 8 9 11 13 15 18 



Largest flower 



in mm. 26 25 27 26 25 26 26 24 26 



Smallest flower 



in mm. 21 20 23 21 22 21 21 21 17 



Daily aver- 

 age in mm. 24 23.8 24.8 23.7 23.6 23.2 23.9 22 24.2 



Date 1911 Oct. 20 27 30 Nov. 13 6 8 18 20 



Largest flower 



in mm. 27 25 25 26 25 25 25 23 22 



Smallest flower 



in mm. 19 20 19 19 17 IS 18 19 19 



Daily aver- 

 age in mm. 22.9 23.8 23.6 19.7 21.7 22.8 23.2 21.6 20.8 



Thus on a single plant of the hybrid IIIJX I cf we obtain 

 the extremes of fluctuation — 17 mm. and 27 mm. — which the 

 flowers of the entire group of plants representing this cross dis- 

 played. As has been said above, this was true throughout all 

 the h^-brid groups — i.e., practically every plant of a hybrid 

 group exhibited in its flowere the extremes of variation in cor- 

 olla diameter reported for the whole hybrid group. It might 

 have been possible that toward the end of the flowering season 

 the fluctuation in corolla diameter would be diminished or that 

 the full effect of the amount of acquired characters might ex- 

 hibit itself (Lang, 1908; see also Groth, 1911, p. 8; Moore, 1910, 

 1912). As will be seen from the above table and plate 33, the 



