a H. Shull 101 



characters makes such subsidiary hypotheses of no value except as a 

 basis for further investigations. 



Other Oenothera crosses are cited, which indicate that the inverse 

 relation between the red-pigmentation of the buds and that of the 

 stems is not limited to crosses of 0. ruhricalyx. Oenothera ruhrinervis 

 represents a progressive variation in the pigmentation of the bud-cones 

 and a retrogressive variation in the pigmentation of the stems. 



It is held that three conclusions arrived at by Gates regarding the 

 origin and genetic nature of the ri(6ricai;(/*'-character are erroneous, 

 namely, (a) that the character represents a purely quantitative differ- 

 ence from 0. ruhrinervis, (b) that it differs from the latter species in 

 a single monohybrid Mendelian unit, and (c) that the nature of a 

 character itself instead of the nature of the inheriting-mechanism to 

 which it is related, determines the manner of inheritance of that 

 character. 



LEGENDS FOR PLATES. 



PLATE V. 



Bosettes of 0. ruhricalyx (upper series), 0. riibrinenus (lower series) and of their 

 reciprocal Fi hybrids. Each set of 3 hybrid rosettes stands next to those of the 

 seed-parent type. Inside diameter of pots about 7'5 cm. Photographed April 19, 1913, 

 about 11 weeks after the seeds were sown. 



PLATE VL 



Eosettes of 0. ruhricalyx (upper series), 0. Lamarckiana (lower series) and of their 

 reciprocal Fj hybrids. Arrangement the same as in Plate V. Photographed April 9, 

 1913, about 10 weeks after the seeds were sown. 



LITERATURE CITED. 



Baur, E. 1910. "Untersuchungen iilier die Vererbuiig von Chromatophoren- 

 merkmalen bei Melaudrium, Antirrhinum und Aquilegia. Zeitschr. f. ind. 

 Abstamm. u. Vererh. Bd. iv. pp. 81 — 102. 



Heribert-Nilsson, N. 1912. "Die Variabilitat der Oenothera Lamarckiana und 



das Problem der Mutation." Zeitschr. f. ind. Abstamm. u. Vererh. Bd. viii. 



pp. 89—231. 

 Gates, R. R. 1909. " An Analytical Key to .some of the Segregates of Oenothera." 



Ann. Rep. Missouri Bot. Gard. Vol. XX. pp. 123 — 137. See p. 133. 

 . 1910. "The Material Basis of Mendehan Phenomena." Amer. Nat. Vol. 



XLiv. pp. 203—213. 



7—3 



