1916] DEVRIES—DIMORPHIC MUTANTS 267 
type remained small, their leaves reaching only about half the 
length and half the breadth of those of their sisters (73 cm. 
against 145 cm.). Their blades were sharply set off from the 
winged petioles (fig. 5, C), and thereby they much resembled those 
of O. pallescens (fig. 4). This resemblance continued during the 
development of the stem and the flower spikes; but even as the 
rosettes were smaller and more densely leaved, the stems were 
lower and weaker and less branched. The leaves were narrower 
and folded along the middle vein, instead of being broad and flat- 
tened, as in O. pallescens. The flower buds were as thick and as 
large as those of this species, and the flowers also reached the same 
size, the petals having a length of 4 cm. During the flowering 
period the differences from O. pallescens grew gradually less, and 
at the end, in September, the new type seemed to be only a weak 
form of this latter, reaching a less height and being almost un- 
branched. Artificial self-fertilization has been difficult, since in 
many flowers the pollen was in an imperfect condition. Four 
specimens yielded a sufficient harvest (0.5-1cc.). The sister 
plants of the Lamarckiana type showed an abundance of seed, 
exactly as the Lamarckiana of pure origin does. 
The next year (1915) I sowed the seeds of one specimen of the 
parental type and of two of the type of Lamarckiana. The first 
gave only 44 seedlings, of which 4 were Lactuca, one nanel.a, and 
the others Lamarckiana. The two other sowings gave 248 and 283 
offspring of their own type, without any Lactuca specimens, but 
with some dwarfs. The number of them was 11, or 4 per cent in the 
first group, but only one in the latter group. Combining these 
results we get the following pedigree: 
so Lk CN eae aS Mutant Mutant 
104 4... First generation 43 per cent Lactuca Lamarckiana 
ce ga ee a Second generation 9 per cent Lactuca Lamarckiana Lamarckiana 
Although only two generations from the seeds of the original 
mutant have been cultivated, it is evident that this new form 
behaves exactly like the inconstant races of O. scintillans, O. cana, 
and O. pallescens. Under favorable conditions it splits into about 
