Igto] BLODGETT—BULBS OF ERYTHRONIUM 341 
differences found have a probable bearing upon the evolution of 
the genus. 
Material was killed in chromacetic acid, and cut usually 10 # in 
thickness; except in the case of the hard seeds, no special methods 
were necessary. 
To Professor DuncAN S. JoHNSON the author wishes to express 
his thanks for helpful criticism and maintained interest during 
the progress of the work. 
Germination 
The flowers of Erythronium americanum appear during the first 
week of April in this region, and the seeds ripen early in June, 
from which seedlings arise the following March. The main body 
of the seed measures about 4X2 mm., but a spongy spur at the 
chalaza and a fleshy raphe nearly double the bulk of the seed, 
subject to individual variation. The embryo in the ripe seed is 
slightly pointed toward the micropyle, but is otherwise undiffer- 
entiated (fig. 1). 
Germination begins about the middle of September, when the 
seed becomes moistened by the fall rains, and the embryo begins 
to elongate. The growing embryo enlarges first to occupy the 
space filled by the spongy endosperm, in which it is imbedded, 
ordinarily by the first week of October. The tip of the cotyledon 
is organized into a haustorial organ, by which the hard endosperm 
is absorbed. Elongation proceeds slowly during the fall, so that 
the embryo is half the length of the seed in December (fig. 2). 
The rate of growth seems to be closely related to the abundance 
of moisture in the soil. The tip of the radicle is pushed about the 
end of the year through the micropyle. The stem apex at this 
Stage appears in a narrow cavity extending from the surface nearly 
‘to the center of the tissue just behind the radicle. The hypocotyl 
does not elongate, and is practically absent. As the embryo con- 
tinues to elongate, the stem apex is carried forward, and retains 
a Constant position in relation to the radicle during the elongation 
of the cotyledon (fig. 3). The zone of elongation during this time 
is in the lower part of the cotyledon, just above the cavity in which 
the stem apex is situated. Growth is nearly vertical, and after 
penetrating the soil 1-3 cm. the descending axis comes to rest. 
