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

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 short-styled form the anthers are attached near the mouth of the tube, and therefore stand above the stigma, which is seated in about the middle of the tubular corolla. The corolla itself is of a different shape in the two forms; the throat or expanded portion above the attachment of the anthers being much longer in the long-styled than in the short-styled form. Village children notice this difference, as they can best make necklaces by threading and slipping the corollas of the long-styled flowers into one another. But there are much more important differences. The stigma in the long-styled form is globular; in the short-styled it is depressed on the summit, so that the longitudinal axis of the former is sometimes nearly double that of the latter. Although somewhat variable in shape, one difference is persistent, namely, in roughness: in