Studies on the Variability and Heritability of Pigmentation in Oenothera. 359 
under surface at a time when the seedlings are young or before the 
rosettes are quite mature, the two forms may be distinguished with 
little difficulty. The mature rosettes preparing for stalk formation 
frequently lose all their pigment and become for a time absolutely 
Fig. 3. Rosette of O. rubricalyx. Identical with O. rubrinervis morphologically, 
but differing physiologically, in pigmentation. 
indistinguishable from O. rubrinervis. A nearly mature rosette of 
O. rubricalyx is shown in fig. 3. It is indistinguishable from O. rubri- 
nervis in a photograph. 
During the early development of the stems, when the plants are 
one or two feet high and before the buds attain an appreciable size, 
