OENOTHERA GRANDIFLORA AIT. 205 



The percentages in April, as well as those found in August, show 

 that the coefficient of mutation for ochracea is wholly different from 

 that for lorea and from the ordinary coefficients for the mutability 

 of 0. Lamarck iana, 0. biennis, and other species. The average of 

 the three figures for ochracea given in table I is 26 per cent, and this 

 figure is somewhat too low on account of the losses mentioned. It 

 is evident, however, that it differs from normal coefficients of muta- 

 bility in the same way as the mass mutations of Bartlett, and that 

 the production of mut. ochracea from 0. grandiflora must be con- 

 sidered as another instance of this phenomenon. Here the mass 

 mutation is repeated in the succeeding generations of the pure line, 

 and, in addition, mutations into lorea and gigas occur in the usual 

 way. 



0. grandiflora mut. ochracea. — This species is well known as 

 more strictly annual than any other of the same group. In spring 

 it hardly makes any rosettes of radical leaves, but at once produces 

 its stem. So did all my mutants, but especially the ochracea begins 

 to make its stem when still very young and before being planted out. 

 Its foliage is yellowish green, running parallel in this respect to 

 O. suaveolens mut. lutescens (7). Even as in this last one, the leaves 

 are strikingly broader and somewhat shorter than in the parent 

 species. This insufficiency of the green color causes the young 

 plants to stay behind the normal ones in their development, and by 

 June they are much weaker. Afterward the new leaves assume 

 a darker green, and in the fall the difference is often very small. 

 The weakness remains, however, and the stature is low during the 

 flowering period, reaching only 50 cm. in the beginning of July, when 

 the normal plants are 70—80 cm. in height. 



Most of the chlorophyll is developed along the veins. The teeth 

 along the margin usually have red tips. The branches stand out 

 from the stem at wide angles, sometimes almost horizontally. The 

 spikes are loose, but the flowers are large and provided with a rich 

 supply of good pollen; the fruits are cylindrical and often thin. 

 These differences are small, apart from the color, but they are very 

 constant. In fig. 1 they do not show so strikingly as they do on 

 the beds. In consequence of the pale green color of the leaves the 

 stems are thin and their wood is insufficiently developed; they are 

 often seen to decay, beginning in the lower part of the stem. Many 

 specimens are lost from this cause during the summer. 



As given in table I, I cultivated the ochracea through three suc- 

 ceeding generations, starting from the mutants of 1914. Two of 



