oT eet en 
BS I Ale Se a EE a RN Se a a de a a ea oe BO Re he ae ein ea aa 
Ig10] BLODGETT—BULBS OF ERYTHRONIUM 345 
itself is lost as a distinct group of cells. When the scale has so 
far developed that the margins of the leaf rudiment meet in front 
of the median line of the scale, then the apical dome becomes 
distinguishable again. The dome then forms a low mass of cells 
projecting from the face of the axial side of the scale into the space 
inclosed by the united margins. Continued growth soon makes 
the dome more conspicuous, and at the same time readjusts its 
position to a more central point (figs. 10, 12, 13). The tissues of 
the scale rudiment and of the stem apex are nearly alike in their 
staining qualities, and continue to be meristematic until a con- 
siderable size is reached. Thus in the first stages of scale formation, 
the growth in length of the apical dome and the growth in thickness 
of the scale rudiment are so nearly equal that there is no difference 
in staining reaction to aid in separating the two morphologically 
different tissues. It is not until the scale leaf has inclosed the 
apical dome by the forward growth of the margins of the scale, 
that the dome is to be separately recognized. This obscuring of 
the apical dome appears to be a recurring feature in the normal 
development of the bulbs, as the successive bulb scales are formed. 
The dropper grows downward to a distance varying from a 
few millimeters to 4 (rarely 5) cm.; in most cases the dropper is 
about 2.5 cm. in length. This growth is accomplished during the 
period of activity of the cotyledon as a leaf, by which the needed 
starch and other materials are elaborated. At the end of three or 
four weeks of development, the apical bud within the dropper 
Sheath becomes enlarged by the deposit of storage starch, and 
the stem apex with its inclosing bulb scale becomes the primary 
bulb (fig. 14). The seedling dies from the apex of the cotyledon 
backward, gradually involving all tissues except the bulb, which 
thus becomes isolated in the soil. The withered walls of the drop- 
per sheath form a husk about the bulb. In the axil of the dropper 
sheath a bud is formed, which rarely develops. 
During the active descent of the dropper, vascular connection 
from the stem apex to the base of the cotyledon is maintained 
through the bundles in the axial wall of the dropper. This tissue 
is to be regarded as cauline in character, since it terminates in the 
rowing point of the stem. In its earliest stages the vascular 
