8 INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATIONS. 
abnormally crowded for 1.5 cm. Transverse sections of a growing region 
revealed callus over the main tip, just above the pith. The..procambial 
strands about the callus seemed unaffected by the injury to the apical 
meristem and were continuing their activity. Longitudinal sections of 
a second plant (plate v, fig. 7) showed callus at the tip of the main 
axis in the former position of the apical cells. Beneath it tracheze and 
sieve-tubes had differentiated and ran irregularly, many in a transverse 
direction, across the apex. A section of this stem is seen in plate v, fig. 8, 
and shows the callus and the apical conditions. The slight depression 
under the callus is surrounded by a ring-shaped meristem (plate v, fig. 7). 
The tip has evidently been injured, the meristem has spread in a circular 
direction, and has become distributed as aring. As enlargement takes 
place in the tip of the stem, its apex will project as a protuberance of greater 
or less development, showing transverse bundle-elements beneath a mass 
of callus. When unequal growth pushes the callus to one side the ring 
(splits and the stem becomes flattened. The origin of’ the injury which 
induced callus formation is to be found in the surrounding plants. In 20 
rosettes of O. cruciata next these individuals larvee were feeding, and as 
the leaves of one of the three in question were freshly eaten, and as another 
‘contained a larva within the stem in the lower part, these insects were 
undoubtedly the agents which attacked the young tips. 
The relation of certain insects to the cenotheras is known to be a constant 
one, and more than one genus is recognized as parasitic upon them. The 
forms found in Bedford Park and in the experimental grounds are species 
of Mompha, a tiny grayish moth with spotted wings. The eggs are laid 
ee the leafy tips and, later, larvee are abundant in the apices, the capsules, 
-and the pith of stalwart plants. They are particularly common in rosettes 
toward the latter part of the summer, and as they develop many bind 
together the leaves to form a shelter and feed among the tender tissues in 
the winter andagaininthe very earlysummer. Most ofthemeat only young 
leaves and never reach the meristem; many devour and destroy the apical 
tissues; while still others irritate or injure them. They are found not only 
in the rosettes that come from seed, but in those which form in late summer 
at the ends of old branches to carry over a perennial growth. The fasci- 
ated rosettes of late summer frequently appear in pairs,. and it.is.common 
to find callus and inhibition of grawth between the two (plate v, ‘fig. 9). 
The condition of the branch.seems to indicate that the main axis has been 
destroyed and the side-buds injured as they were forced out.. Such branches 
commonly have circular meristems in the pith, surrounding spots of brown 
discoloration of the sort which develop about masses of dead cells. 
A second.kind of injury may arise through the ovipositors of the insects. 
In the pith of woody stems of O. cruciata, O. parviflora, and O: biennis, and 
in the capsules.of ‘O. grandiflora and other forms, are larve closely related 
to those in the rosettes. Those which undergo metamorphosis in the 
