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ledons. The general rule is then “ that the cotyledons are sessile 
when they are raised by the growth of the hypocotyl, while they 
are petiolate when they take their origin close to the ground.” 
Connate petioles serve the purpose of forming a stronger support 
for the cotyledons than would be afforded if they remained separate. 
5. Narrowness of the cotyledons or their division into narrow 
segments is attributed to the greater facility with which they 
may be withdrawn from the seed-coats. Also, narrowness of the 
cotyledons in some cases “ enables the plant to make them lie 
conveniently in a globose seed.” 
The generalizations with which each order is introduced, are 
especially interesting and valuable. Here, as well as in the de- 
scription of each species, the cotyledons are given prominence. 
The Onagrariez is as fair a choice among the orders as could be 
made. The seedlings of quite a number of its species have coty- 
ledons in which a secondary growth occurs. The seedlings of 
nothera Bistorta are described as follows: 
‘Immediately after germination the cotyledons are oblong, 
obtuse, entire, sessile with a few long, scattered, glandular hairs, 
especially at the base. Hypocotyl with a few glandular hairs at 
the apex. Cotyledons often unequal, owing to their greater or 
less development in the seed, and one folding over the other. 
“Six days after germination the base has become elongated, 
petiole-like, and glandular-pubescent, suddenly narrowed to a 
short petiole, or subsessile; the upper half remains rotund and 
glabrous except at the base and possibly a few short hairs under- 
neath. 
“Eight days after germination (fig. 367) they have elongated 3 
considerably, the upper true cotyledonary part enlarging, but 
otherwise remaining unaltered, while the foliar basal and narrow 
part has become linear, entire or sometimes with a minute tooth 
on either side, glandular-pubescent, suddenly narrowed at the very 
base. 
“ The lower portion elongates greatly, and the ultimate stage 
of the cotyledons (fig. 368) is linear, tapering at the base into a 
petiole; upper part or true cotyledon rotund or oval, entire gla- 
brous, very short without midrib, lower part linear terminating 
abruptly in the upper part, tapering gradually to the base, with 
one or two minute and distant teeth on each side, thinly hairy, . 
