12. INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATIONS. 
all of these forms, ‘gathered in from all over the world, nor can it be regarded 
as the sporadic appearance of latent characters. The fact that. in many 
series from normal races, 100 per cent of the individuals ‘planted: out fas- 
ciated, though no selection was exercised in saving the rosettes from the 
large numbers of seedlings originally planted, strengthens the inference 
‘that its development is due to local causes. One is led to conclude that 
there have been. prevalent -in the garden and in this region during the 
summers of 1905 and 1906 swarms of insects whose attacks upon the growing 
tips. were particularly. insidious and stimulative without being at the same 
time destructive.” It happened, too, that several species of the primroses 
were markedly susceptible to the injuries, and that the conditions of light 
and nutriment were favorable to vigorous development. Given similar 
conditions of culture, the factors involved in the production of the fasciations 
are the specific mode of attack of such insects, the character of the plant, 
and the rapidity of development; the second of the three is the most 
important, as it is true that in two adjacent groups of O. diennis, one will 
fasciate and the other will not. It is also true that the form of the fascia- 
tion varies. with the group ‘affected. Thus O. ‘‘muricata’’ from Kansas, 
O. parviflora, O. ammophila,.and O. grandifiora developed simple-banded 
fasciations, while rings and. protuberances appeared on the O. cruciata and 
grooves on the wild O. dennis. . The O. cruciata from the Lake George stock 
differed from the O. cruciata varia (?) from Hamburg, which may be what 
de Vries calls a poor race. Ofthis O. cruciata varia (?) 40 plants sown at the 
same time with the Maine cultures, of which the rosettes were bifurcated, 
failed to show fasciation either.in the rosettes or branches. 
This group of plants floweréd much earlier than the others, which calls 
attention to the importance of the late development of the individual. Most 
of the fasciations date from the period just preceding the opening of the 
flowers in July, and they flatten among masses of fruits, or at-a point where 
the stung flowers have fallen off and left the stem bare. From this'tiine the 
eggs of the momphas are laid, the larvae develop, and new swarms of imagos 
begin to emerge toward the end of the summer, at onee proceeding to sting 
new tips: Those apices which have passed the period of greatest vigor 
gradually dwindle away and dic, but leafy axes, leafy rosettes, stems ready 
to flower through September, all soft tissues in a thriving condition, then 
fasciate in greater abundance proportionately than earlier in the season, 
for their limited number makes it more certain that they will be attacked 
by the recent invasion of the new swarm. In the rosette stage the rate of 
growth is also important. ‘It is seldom that the insect reaches the apical 
meristem of a quick-growing plant, for the rapid formation of new leaves 
supplies sufficient food for the larva, and the formative region remains 
untouched. Sections of numbers of young rosettes containing larvee easily 
prove that the insect ordinarily feeds above the apex or at its side. Though 
plants are often unaffected by the parasites, doubtless swarms occasionally 
