oms developed in spring,
and in which the petals are always present, are much less fertile. In
_Oxalis Acetosella_ there are two forms of flower, the one with, the
other without, petals, but both seem equally fertile. Linne remarks that
many plants which, in warm latitudes, produce a corolla, do not do so
when grown in colder climates. Thus, certain species of _Helianthemum_
are apetalous in Lapland. In the Pyrenees, according to Bentham, the
flowers of _Ajuga iva_ are constantly deprived of their corolla.[481]

Apetalous flowers have been noted most frequently in the following
plants:

Aconitum, sp. pl.!
Cardamine impatiens.
Cheiranthus Cheiri!
Viola odorata!
Cerastium vulgatum!
Alsine media.
Stellaria.
Lychnis dioica!
Dianthus barbatus, and other Caryophylleae.
Helianthemum, sp.!
Oxalis Acetosella.
Balsamineae.
Malpighiaceae.
Rosa centifolia.
arvensis!
Crataegus!
Medicago lupulina.
Melilotus officinalis.
Ononis minutissima.
Saxifraga longifolia.
Verbascum Thapsus.
Ajuga iva.
Teucrium Botrys.
Lamium purpureum!
amplexicaule.
Polemonium caeruleum.
Campanula, sp. pl.!
Ruellia clandestina.
Lonicera Periclymenum!
Tradescantia, sp.!
Hymenocallis.

The following references apply some to apetalous and others to
dimorphic flowers, but it must be remembered that the latter
plants are not necessarily wanting in petals or stamens, &c.,
though the functional activity of the parts may be impaired:

A. de Jussien, 'Monogr. Malpigh.,' pp. 82, 334. Torrey, 'Fl.
New York,' i, p. 428. Hooker and Thomson, 'Journ. Linn. Soc.,'
ii, p. 7, Guillemin, 'Archiv. de Botan.,' i, p. 412. Michalet,
'Bull. Soc. Bot. Fr.,' vii. p. 465. Mueller, 'Bot. Zeit.,' 1857,
p. 729. 'Natural History Review,' July, 1862, p. 235.

=Meiotaxy of the androecium.=--Complete suppression of the stamens
occurs normally in the female flowers of unisexual plants, and, as an
accidental occurrence, is not very uncommon. _Erica Tetralix_ is one of
the plants in which this is said to happen. The variety _anandra_ is
said to have been known in France since 1635. Cornuti speaks of it in
his 'Enchiridion.' In 1860 M. du Parquet discovered it in peaty woods
near Nangis (Seine et Marne).

Many _Umbelliferae_, such as _Trinia vulgaris_, present a like
deficiency, while it is of common occurrence among _Rosaceae_ and
_Pomaceae_. In the latter