Phalaris Canariensis (Gramineae).--With the Gramineae the part which first
rises above the ground has been called by some authors the pileole; and
various views have been expressed on its homological nature. It is
considered by some great authorities to be a cotyledon, which term we will
use without venturing to express any opinion on the subject.* It consists
in the present case of a slightly flattened reddish sheath, terminating
upwards in a sharp white edge; it encloses a true green leaf, which
protrudes from the sheath through a slit-like orifice, close beneath and at
right angles to the sharp edge on the summit. The sheath is not arched when
it breaks through the ground.
The movements of three rather old seedlings, about 1 ? inch in height,
shortly before the protrusion of the leaves, were first traced. They were
illuminated exclusively from above; for, as will hereafter be shown, they
are excessively sensitive to the
* We are indebted to the Rev. G. Henslow for an abstract of the views which
have been held on this subject, together with references.
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