NOTES ON HETEROPHYLLY. 123
stiff green and woody shoots, are reduced to single narrow leaflets
or to mere scales.
Our common Tamarisk (Tamarix gallica) has the foliage of
young shoots longer and more loosely arranged than that on the
later mature branchlets with their closely braided scale-leaves.
The contrast is more striking in the Chinese Tamarisk (T. juni-
perina). A large tree of this species, nearly thirty feet high
and with a trunk sixteen inches in girth, is trained over an
archway in the First Court of Trinity College, Cambridge. We
saw it one spring, when our Field Club was visiting Cambridge,
after the branches had been cut back the previous autumn; it
had sent out a few strong erect shoots thickly clothed with
strap-shaped leaves 0.15 to 0.25 inch long. It was not till
months later, when the typical feathery drooping sprays, covered
with minute leaves, had appeared, that we learnt the name of
the plant.
The Holm Oak or Holly Oak, Quercus Ilex, bears at first such
prickly leaves that seedling plants have been mistaken for
those of Holly; more or less spine-toothed leaves occur on the
lower branches of the mature tree while the upper leaves are as
entire as those of the Olive, which they resemble. The leaves
on the suckers of the Aspen and Grey Poplar are strikingly
different from those on the upper branches.
The Common Mulberry, Morus nigra, shows some hetero-
phylly. Usually the leaves are ovate, deeply cordate and sym-
metrical, but branches occur with many leaves irregularly lobed.
After a bough has been cut back the shoots arising from its base
bear deeply lobed leaves. I do not know if the seedling plants
have similarly lobed leaves.
Heterophylly may occur on shrubs and trees in a way un-
connected with the age of the plant. The fragrant flowered
shrub Osmanthus Fortunei, from Japan, has both entire and
spinose leaves on the same branches; the Chinese Forsythia
suspensa has both entire and trifoliate leaves on the same spray;
the Woody Nightshade, Solanum nigrum, also has entire and
deeply lobed leaves on the same shoot.
Our woody climber, Ivy, shows an amazing variety in leaf-
shape, having often three- to five-lobed leaves on the creeping
stems, and broadly ovate entire leaves on the bush form. When
the late distinguished American botanist, Asa Gray, came to