Cucumis dudaim (Cucurbitaceae).--Two seedlings had opened
[page 44]
their cotyledons for the first time during the day,--one to the extent of
90o and the other rather more; they remained in nearly the same position
until 10.40 P.M.; but by 7 A.M. on the following morning the one which had
been previously open to the extent of 90o had its cotyledons vertical and
completely shut; the other seedling had them nearly shut. Later in the
morning they opened in the ordinary manner. It appears therefore that the
cotyledons of this plant close and open at somewhat different periods from
those of the foregoing species of the allied genera of Cucurbita and
Lagenaria.
Fig. 31. Opuntia basilaris: conjoint circumnutation of hypocotyl and
cotyledon; filament fixed longitudinally to cotyledon, and movement traced
during 66 h. on horizontal glass. Movement of the terminal bead magnified
about 30 times, here reduced to one-third scale. Seedling kept in
hot-house, feebly illuminated from above.
Opuntia basilaris (Cacteae).--A seedling was carefully observed, because,
considering its appearance and the nature of the mature plant, it seemed
very unlikely that either the hypocotyl or cotyledons would circumnutate to
an appreciable extent.
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