The Different Forms of Flowers on Plants of the Same Species | Page 9

of
the flowers include pistils, but these likewise drop off at an early period;
and the ovules, which ultimately abort, are very small compared with
those in female flowers of the same age.
Of the other or monoicous sub-group of polygamous plants, or those
which bear hermaphrodite, male and female flowers on the same
individual, the common Maple (Acer campestre) offers a good instance;
but Lecoq states that some trees are truly dioecious, and this shows

how easily one state passes into another. (Introduction/19. 'Geographie
Botanique' tome 5 page 367.)
A considerable number of plants generally ranked as polygamous exist
under only two forms, namely, as hermaphrodites and females; and
these may be called gyno- dioecious, of which the common Thyme
offers a good example. In my seventh chapter I shall give some
observations on plants of this nature. Other species, for instance several
kinds of Atriplex, bear on the same plant hermaphrodite and female
flowers; and these might be called gyno-monoecious, if a name were
desirable for them.
Again there are plants which produce hermaphrodite and male flowers
on the same individual, for instance, some species of Galium, Veratrum,
etc.; and these might be called andro-monoecious. If there exist plants,
the individuals of which consist of hermaphrodites and males, these
might be distinguished as andro-dioecious. But, after making inquiries
from several botanists, I can hear of no such cases. Lecoq, however,
states, but without entering into full details, that some plants of Caltha
palustris produce only male flowers, and that these live mingled with
the hermaphrodites. (Introduction/20. 'Geographie Botanique' tome 4
page 488.) The rarity of such cases as this last one is remarkable, as the
presence of hermaphrodite and male flowers on the same individual is
not an unusual occurrence; it would appear as if nature did not think it
worth while to devote a distinct individual to the production of pollen,
excepting when this was indispensably necessary, as in the case of
dioecious species.
I have now finished my brief sketch of the several cases, as far as
known to me, in which flowers differing in structure or in function are
produced by the same species of plant. Full details will be given in the
following chapters with respect to many of these plants. I will begin
with the heterostyled, then pass on to certain dioecious, sub-dioecious,
and polygamous species, and end with the cleistogamic. For the
convenience of the reader, and to save space, the less important cases
and details have been printed in smaller type [].
I cannot close this Introduction without expressing my warm thanks to

Dr. Hooker for supplying me with specimens and for other aid; and to
Mr. Thiselton Dyer and Professor Oliver for giving me much
information and other assistance. Professor Asa Gray, also, has
uniformly aided me in many ways. To Fritz Muller of St. Catharina, in
Brazil, I am indebted for many dried flowers of heterostyled plants,
often accompanied with valuable notes.
CHAPTER I.
HETEROSTYLED DIMORPHIC PLANTS: PRIMULACEAE.
Primula veris or the cowslip. Differences in structure between the two
forms. Their degrees of fertility when legitimately and illegitimately
united. P. elatior, vulgaris, Sinensis, auricula, etc. Summary on the
fertility of the heterostyled species of Primula. Homostyled species of
Primula. Hottonia palustris. Androsace vitalliana.
(FIGURE 1.1. Primula veris. Left: Long-styled form. Right:
Short-styled form.)
It has long been known to botanists that the common cowslip (Primula
veris, Brit. Flora, var. officinalis, Lin.) exists under two forms, about
equally numerous, which obviously differ from each other in the length
of their pistils and stamens. (1/1. This fact, according to Von Mohl
'Botanische Zeitung' 1863 page 326, was first observed by Persoon in
the year 1794.) This difference has hitherto been looked at as a case of
mere variability, but this view, as we shall presently see, is far from the
true one. Florists who cultivate the Polyanthus and Auricula have long
been aware of the two kinds of flowers, and they call the plants which
display the globular stigma at the mouth of the corolla, "pin-headed" or
"pin-eyed," and those which display the anthers, "thrum-eyed." (1/2. In
Johnson's Dictionary, "thrum" is said to be the ends of weavers' threads;
and I suppose that some weaver who cultivated the Polyanthus invented
this name, from being struck with some degree of resemblance between
the cluster of anthers in the mouth of the corolla and the ends of his
threads.) I will designate the two forms as the long-styled and
short-styled.

The pistil in the long-styled form is almost exactly twice as long as that
of the short-styled. The stigma stands in the mouth of the corolla or
projects just above it, and is thus externally visible. It stands high above
the anthers, which are situated halfway down the tube and cannot be
easily seen. In the