INDUCTION, DEVELOPMENT, AND HERITABILITY OF FASCIATIONS. 7 
is represented in fig. 1; a later stage in fig. 2 shows the character of the 
meristematic groups embedded in thick-walled parenchyma, and in fig. 3 
the gradual differentiation into phloem and xylem is pictured. Interme- 
diate between the ring and the groove types is found an example illustrated 
in plate Iv, series 4, of what is classed by Nestler (8) in V. longifolia as 
an ‘‘imperfect ring.’’ In this the meristems arise in the pith, a ring of 
bundles develops there, and the ring passes over to one side until it touches 
the primary bundle-ring, with which it then fuses. At this point the flat- 
tening of the stem first becomes marked. In one individual the lysigenous 
cavity, characteristic of the ring-fasciations, formed within the second 
bundle-ring and passed out into the cortex when the two bundle-rings 
merged. Stems with the protuberances on the plants of O. cruciafa when 
sectioned (plate iv, series 2) reveal conditions similar to those of the two 
types preceding. The medullary parenchyma cells in the center of the 
stem become smaller and more closely crowded together. A meristem then 
arises in the pith and, after differentiating into a secondary bundle-ring, 
becomes part of the primary ring, as in the intermediate or ring-groove 
type. The composite ring then bulges out at the point of fusion, and a 
portion of it is cut off to form the protuberance. This cylindrical process 
(plate v, fig. 4) possesses a woody bundle-ring, but there is no apical 
meristem and, near the tip, primary trachee and sieve-tubes run irregularly 
across its axis (plate v, fig. 6). Above this are irregular, yellowish callus 
cells (plate v, fig. 5). In avery common variant of its structure, serial 
sections show, in the pith below the protuberance, a group of cells formed 
of tracheze and sieve-tubes, which run transversely and in great confusion. 
As this group passes toward the periphery and touches the primary bundle- 
ring the regularity of arrangement is disturbed in the latter, and is only 
restored after the knob has been entirely cut off fromthe stem. In another 
variant the meristem does not appear below the protuberance, nor does 
the stem fasciate. Ina case of this kind the cortex around the main stem 
was found to be eaten off by insects, the growing region injured, and the 
lower buds forced out. This is simple abortion of the main axis, with 
destruction of leaves and buds, which leaves the surface of the aborted 
stem in the form of a hard and smooth projection. The variations of these 
regions, of which there may be said to be almost as many as there are 
specimens, together with the variations of the rings and grooves, are all 
manifestations of the same principle. The early conditions of one are 
doubtless similar to the conditions of all, and for this reason special interest 
attaches itself to the young stages of any of them. 
A young protuberance with accompanying fasciation was found in a stem 
of O. cruciata, illustrated in plate m1, fig. 6, which was cut in September 
from one of three slow-growing plants which had elongated 20 cm. from 
the rosette stage. The phyllotaxy was disturbed for 3cm., and the leaves 
