12 INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATlONvS. 



all of these forms, s'athered in from all over the world, nor can it be reg-arded 

 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 origfinally i^lanted, 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 rnarkedly 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. biennis, 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. grandiflora developed simple-banded 

 fasciations, while rings and protuberances appeared on the 6>. cruciata and 

 g-rooves on the wild O. biennis. The O. cruciata from the Lake George stock 

 differed from the O. cruciata varia if) from Hamburg-, which maybe what 

 de Vries calls a poor race. Of this O. cruciata varia (f) 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 grroup of plants flowered 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 time the 

 eg-g-s of the momphas are laid, the larvae develop, and new swarms of imag-os 

 begin to emerg-e toward the end of the summer, at once proceeding- to sting- 

 new tips. Those apices which have passed the period of greatest vig-or 

 gradually dwindle away and die, 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 

 imtouched. Sections of numbers of young ro.settes containing larvae easily 

 prove that the insect ordinarily feeds above the apex or at its side. Though 

 plants are often unaftected by the parasites, doubtless swarms occasionally 



