pumilio_, with its several sub-varieties, as _Mughus_, _nana_, &c.,
which differ much when planted in different soils and only come
"tolerably true from seed," as alpine varieties of the Scotch fir; if
this were proved to be the case, it would be an interesting fact as
showing that dwarfing from long exposure to a severe climate is to a
certain extent inherited.

The _Hawthorn_ (_Crataegus oxycantha_) has varied much. Besides endless
slighter variations in the form of the leaves, and in the size,
hardness, fleshiness, and shape of the berries, Loudon[779] enumerates
twenty-nine well-marked varieties. Besides those cultivated for their
pretty flowers, there are others with golden-yellow, black, and whitish
berries; others {364} with woolly berries, and others with recurved
thorns. Loudon truly remarks that the chief reason why the hawthorn has
yielded more varieties than most other trees, is that curious
nurserymen select any remarkable variety out of the immense beds of
seedlings which are annually raised for making hedges. The flowers of
the hawthorn usually include from one to three pistils; but in two
varieties, named _Monogyna_ and _Sibirica_, there is only a single
pistil; and d'Asso states that the common thorn in Spain is constantly
in this state.[780] There is also a variety which is apetalous, or has
its petals reduced to mere rudiments. The famous Glastonbury thorn
flowers and leafs towards the end of December, at which time it bears
berries produced from an earlier crop of flowers.[781] It is worth
notice that several varieties of the hawthorn, as well as of the lime
and juniper, are very distinct in their foliage and habit whilst young,
but in the course of thirty or forty years become extremely like each
other;[782] thus reminding us of the well-known fact that the deodar,
the cedar of Lebanon, and that of the Atlas, are distinguished with the
greatest ease whilst young, but with difficulty when old.

FLOWERS.

I shall not for several reasons treat the variability of plants which
are cultivated for their flowers alone at any great length. Many of our
favourite kinds in their present state are the descendants of two or
more species crossed and commingled together, and this circumstance
alone would render it difficult to detect the differences due to
variation. For