According to the current views the
families with the petals of their flowers united are regarded as one or
two main branches of the whole pedigree of the vegetable kingdom.
Eichler and others assume them to constitute one branch, and therefore
one large subdivision of the system. Bessey, on the other hand, has
shown the probability of a separate origin for those groups which have
inferior ovaries. Apart from such divergencies the connation of the
petals is universally recognized as one of the most important systematic
characters.
How may this character have originated? The heath-family or the
Ericaceae and their nearest allies are usually considered to be the
lowest of the gamopetalous plants. In them the cohesion of the petals is
still subject to reversionary exceptions. Such cases of atavism may
[661] be observed either as specific marks, or in the way of anomalies.
_Ledum_, _Monotropa_ and _Pyrola_, or the Labrador tea, the Indian pipe
and wintergreen are instances of reversionary gamopetalism with free
petals. In heaths (_Erica Tetralix_) and in rhododendrons the same
deviation is observed to occur from time to time as an anomaly, and even
the common _Rhododendron ponticum_ of our gardens has a variety in which
the corolla is more or less split. Sometimes it exhibits five free
petals, while at other times only one or two are entirely free, the
remaining four being incompletely loosened.
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