INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATIONS. 9 
capsules of O. grandiflora are Mompha brevivitella, known at one time as 
Laverna enotherevorella, and in May and again in July the insects are 
constantly invading thetips. The slightest irregularity in the arrangement 
of the young leaves during or just preceding the flowering period, an 
appearance like that shown in plate 11, fig. 2, or such as might result from 
some external mechanical interference, indicates that the tip when sectioned 
will prove to be fasciated or bifurcated. There is no sign externally of the 
fasciated outline in these tiny tips, merely reddish color, inequality of 
development, or a tiny aperture suggesting acallus. Microscopical exam- 
ination proves ring-fasciations and protuberances to be abundant, and simple 
fasciations occasional. The development at this stage covers less than 
5mm. of the stem, but is none the less perfect. Two such apices are 
diagrammed in plate v, figs.10and13. Inmany tipsare found long, needle- 
like incisions, illustrated in plate v, figs. 11, 12, and 13, as if made by an 
ovipositor. About these the cells have hypertrophied, and cylindrical meri- 
stems are forming. Throughout the stems at intervals are small areas 
surrounded. by hypertrophies and meristematic conditions (plate v, fig. 15). 
These are akin morphologically to the meristems in the pith of the old 
rosettes, and are like those about the track of the larve in stems in which 
the pith is infested with the latter. All of them are readily recognizable 
because of the purplish intercellular secretions, seen in plate v, figs. 11, 
12, 14, 15, and the changes are those which customarily follow in the 
neighborhood of dead cells. Tips of this appearance collected July 27, 
1906, were bifurcated, if not definitely fasciated; none of them were normal; 
and there were ‘‘stings’’ of various sorts in them all. 
The anatomical structure of rings and grooves and of the protuberances 
proves them to be variations of a single type, for the essential features of 
their development are the same. The protuberance varies so greatly in 
its structure and in its morphology that its simplest form is a mere callus 
associated with a few irregular bundle-elements projecting from the side 
of the stem (plate m1, fig. 4, and plate v, fig. 10, &). It is easy to conceive 
cases in which the injury is so small as to be impossible of detection. 
Incisions in young meristems are quickly obliterated by the turgidity and 
growth of the surrounding cells (plate v, fig. 12), and it may be assumed 
that many fasciations are caused by injuries too delicate to follow in any 
but the initial stages. Only chance enables one to find such stages, and 
innumerable tips may be sectioned without avail. To a stimulus of this 
nature, obscure in its histological effects, the simple fasciations must owe 
their origin. They occur on the same plants with those more easily detected, 
and may themselves, when bifurcated, be recognized while comparatively 
young. Yet the stimulus is slow to produce the abnormal condition, and 
the irritating cause is concealed before the effect is seen. In a tip of 
O. biennis which contained an active larva, a group of very small paren- 
chyma cells had differentiated in the pith. This is the condition that 
