Therefore in different
individuals of this same species of Acanthus the first pair of leaves
breaks through the ground by two widely different methods; and if
[page 80]
either had proved decidedly advantageous or disadvantageous, one of them no
doubt would soon have prevailed.
Asa Gray has described* the peculiar manner of germination of three widely
different plants, in which the hypocotyl is hardly at all developed. These
were therefore observed by us in relation to our present subject.
Delphinium nudicaule.--The elongated petioles of the two cotyledons are
confluent (as are sometimes their blades at the base), and they break
through the ground as an arch. They thus resemble in a most deceptive
manner a hypocotyl. At first they are solid, but after a time become
tubular; and the basal part beneath the ground is enlarged into a hollow
chamber, within which the young leaves are developed without any prominent
plumule. Externally root-hairs are formed on the confluent petioles, either
a little above, or on a level with, the plumule. The first leaf at an early
period of its growth and whilst within the chamber is quite straight, but
the petiole soon becomes arched; and the swelling of this part (and
probably of the blade) splits open one side of the chamber, and the leaf
then emerges.
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