14 MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 



4 to 45 per cent of the progeny, or an average of 22 per cent. In the cultures 

 made in New York, /a/a, if present, was mistaken for lamarckiana in the seed- 

 ling stage and was discarded. Among the plants of this progeny which were 

 finally brought to bloom were albida, oblonga, nanella, and another type not 

 recognizable by the authors. 



La/a is to be regarded as a retrogressive departure from the parental type, 

 and is most readily recognized by the rounded leaves of the rosettes, and these 

 organs become very much crinkled in later stages of development. The 

 leaves are of a deep green, and the flower-buds are much thicker than any 

 other evening-primrose known, except gigas, perhaps. 



The principal taxonomic characters are as follows: The general habit of 

 this species resembles that of 0. gigas more nearly than any other of the 

 mutants, being sparingly branched, and having short, stoutish branches on 

 the upper portion of the stem. All of the branches are ascending, and in 

 many of the plants the terminal portion of the stem is bent over. 



The stem is channeled and angled, brittle, and both stems and branches 

 are hirsute. The stem-leaves are finely pubescent, 10 to 15 cm. long, 4 to 5 

 cm. wide, numerous, and with the laminae remotely and shallowly toothed. 

 The leaves of the rosettes, even in the very early stages, are noticeably rounded 

 and obtuse at the apex, and those of the lower part of the stem are spatulate- 

 oblong and vary to ovate-oblong on the upper portions of the stem. Those 

 on the upper part of the stem are either obtuse or acutish at the apex and 

 taper to a margined petiole at the base. The leaves, even in young rosettes, 

 are closely bunched into a head and are so heavily crinkled and thrown into 

 convexities and concavities between the veins as to be easily distinguishable 

 from all other forms in all stages of development. 



The bracts are large, ovate to ovate-oblong, acute' or obtuse at the apex, 

 cordate or subcordate, and clasping at the base. 



The conic portions of the heavy buds are 2 cm. long and i cm. in diameter in 

 the basal portion, tapering so slightly as to appear nearly cylindrical, and are 

 finely pubescent with spreading hairs. The free tips of the buds are spreading, 

 stout, 4 to 5 mm. long. The hypanthium is about 35 mm. long, stout, finely 

 pubescent and much longer than the reflexed sepals (plate 4 and plate 5, A). 



The petals are thick, crinkled, and do not expand fully, being about 35 to 40 

 mm. long, and 45 to 50 mm. wide. The filaments are 18 to 20 mm. long, 

 while the anthers are imperfect, being very slender and about 8 mm. in length. 

 The microscopical examination of the anthers showed a few pollen grains 

 apparently perfect, yet no fertilization has ever been accomplished with them 

 in Amsterdam. 



In a recent paper R. R. Gates (1907) describes the results of an investigation 

 of the pollen development of 0. /a/a in which he ascribes the failure of the 



