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THE ESSEX NATURALIST.
Another member of the family Alismaceoe bearing leaves
of different shapes, is the Arrowhead, Sagittaria sagittifolia,
a plant common in canals, and slow streams, and abundant
in the Roding. The floating leaves are oval, and the aerial leaves
arrow-shaped. The submerged leaves are ribbonlike and trans-
lucent with blunt rounded ends, and may grow to be a yard long.
Where the current is too swift for the arrow-shaped leaves to
grow, these submerged ribbons often form great beds swaying
in the stream, and may be puzzling to identify unless an arrow
leaf is near by to give a clue. With a lens they may be
distinguished from other ribbon-leaves by the venation. The
FIG. 2.
midrib is slightly emphasized and usually there are two parallel
lateral veins, from which oblique branches are given off, espec-
ially near the tip. One side of the leaf has a tendency to grow
more vigorously than the other, the result being that the leaves
often have a slight spiral twist. The whorls of large flowers
with white, purple-based petals, purple anthers and golden
pollen are probably familiar to all of us; the stamens and pistils
usually grow on different flowers; the spiky balls of ripe fruit
roughly resemble those of Bur-reed. In autumn reserves of
food are stored in the corm at the base of the stem and also
in tubers borne on long underground runners. These tubers
are striking-looking objects; they are round, peacock-blue