G. H. SHULL 95 



(6) 10 [18] with bright red stems, very slightly reddened bud-cones 

 and green hypanthia. 



(c) 2 [3] with pink stems, and with cones and hypanthia red 

 throughout. 



(d) 5 [5] with stems nearly green and buds entirely green. 



A plant of the type (6), which type made up the bulk of the F 1 

 family, pollinated by a plant of the parental biotype of 0. cruciata 

 (i.e., a sesqui-reciprocal hybridization of the form ( A x B) x A), produced 

 43 [97] offspring with red hypanthia and red cones on pink stems, and 

 5 [6] with faint reddening on the cones, green hypanthia and intensely 

 red stems (Fed. No. 12107). The parental form of 0. cruciata had only 

 moderate reddening of the stems, so that the red stems of the hybrid 

 types (a) and (5) represent a marked intensification of the pigmentation 

 as compared with both parents, just as the red hypanthia and strongly 

 red-pigmented bud-cones of hybrid type (c) show a remarkable advance 

 over the pigmentation of the buds in 0. Lamarckiana, the only one of 

 the parents which had any red coloration of the buds. 



In crosses between 0. Lamarckiana and two other biotypes of 

 0. cruciata, the F-^ hybrids, when 0. Lamarckiana is the mother, are in 

 each cross of uniform type, having the bud-cones reddened to about the 

 same extent as in 0. rubrinervis (i.e., much more strongly reddened 

 than in 0. Lamarckiana) while all the vegetative parts are pale green 

 and absolutely devoid of red-pigmentation. The reciprocal crosses 

 produced in the one case two types, in the other case four types, some 

 of which had pink cones and green hypanthia, others entirely green 

 buds, but all had strongly reddened stems, the green-budded plants 

 having a stronger pigmentation of the stems than the pink-coned plants. 

 In the latter pedigrees the green-budded forms can be partially sorted 

 out from the pink-coned forms in the rosette -stage, because of the more 

 prominent red spots on the dorsal surface of the young rosette-leaves 

 in the former. 



The pigmentation of 0. rubrinervis as compared with its parent 

 0. Lamarckiana, may be related to the same phenomenon, for the bud- 

 cones of the mutant- form are much more strongly pigmented than those 

 of 0. Lamarckiana, while the rosettes are entirely free from red spots 

 and the stems are nearly green, while 0. Lamarckiana, on the other 

 hand, has the rosettes sparsely spotted and the stems moderately 

 reddened. Thus, 0. rubrinervis shows a progressive variation in the 

 amount of red pigment in the buds, while the leaves and stems present 

 a retrogressive variation in respect to red pigmentation. 



