2 
The akene is one-celled, containing a single anatropous, ex- 
albuminous seed with a straight embryo. The embryo conforms 
in shape and size to the enclosing walls. In Bidens and Coreopsis 
it is much flattened and narrows abruptly at ‘the base; in upa- 
torium and Mikamia it is cylindrical; and in Helianthus, Aster and 
Solidago and many others it is top-shaped, the cotyledons filling 
the upper thicker portion of the akene, and these narrowed be- 
low into the still narrower hypocotyl. The cotyledons are usually 
longer and broader than the hypocotyl, but this is not always the 
case, (as asserted in Gray’s Syn. Fl. of N. A., p. 48). In Ambrosia 
the hypocotyl is very small; in As¢er, Solidago, and Coreopsis 
the hypocotyl is larger, but still is much shorter and narrower 
than the cotyledons; in Expatorium and Mikania it is as long, or 
longer than the cotyledons, and is nearly, if not quite as broad. 
The plumule is minute, but may be seen in a vertical section of the 
seed. The cotyledons are closely applied to each other, their 
faces being in the same plane in which the seed is flattened. 
Germination begins by the growth of the hypocotyl, and its 
first evidence is the protrusion of that organ through the aperture 
at the base of the akene. The cotyledons enlarge, sometimes 
splitting the akene and thereby emerging; sometimes, especially 
in those cases where the akene is small, withdrawing entirely, and 
leaving the akene a mere shell. Akenes planted out doors in 
autumn germinate promptly in the spring. 
The seedling always has two cotyledons which are nearly or 
quite alike. They vary in size from an inch long in Ambrosia 
trifida and Helianthus annuus to minute in the Artemisias and 
Chrysanthemums. They are all the way from nearly sessile in 
Chrysanthemum and Anthemis to long-petioled in Prenanthes and 
Arctium. The bases of the petioles form a sheath around the 
plumule when the seedling is young. This sheath is widely 
dilated in An¢hemis, but in most cases appears as a continuation of 
the hypocotyl. The cotyledons, although differing in some 
respects, display a striking uniformity throughout the order. They 
| vary from spatulate to orbicular; in a majority of cases, however, 
being oblong. They are entire and usually narrowed abruptly 
into the petiole. The midvein is usually prominent, and may run 
to the apex or may fork somewhat below. In some species two 
