Accidental variations in both directions occur. The Canada fleabane or
_Erigeron canadensis_, the tansy or _Tanacetum vulgare_ and some others
may at times be seen with ray-florets, and according to Murr, they may
sometimes be wanting in _Aster Tripolium_, _Bellis perennis_, some
species of _Anthemis_, _Arnica montana_ and in a number [237] of other
well-known rayed species. Another instance may be quoted; it has been
pointed out by Grant Allen, and refers to the dead-nettle or Lamium
album. Systematically placed in a genus with red-flowering species, we
may regard its white color as due to the latency of the general red
pigment.
But if the flower of this plant is carefully examined, it will be found
in most cases not to be purely white, but to have some dusky lines and
markings on its lower lip. Similar devices are observed on the lip of
the allied _Lamium maculatum_, and in a less degree on the somewhat
distant _Lamium purpureum_. With _Lamium maculatum_ or spotted
dead-nettle, the affinity is so close that even Bentham united the two
in a single species, considering the ordinary dead-nettle only as a
variety of the dappled purple type. For the support of this conception
of a specific or varietal retrograde change many other facts are
afforded by the distribution of the characteristic color and of the
several patterns of the lips of other labiates, and our general
understanding of the relationships of the species and genera in this
family may in a broad sense be based on the comparison of these
seemingly subordinate characteristics.
Pages:
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241