In the best account which I have seen, it is stated that many of the varieties in the United States consist of three forms, namely, females, which produce a heavy crop of fruit,--of hermaphrodites, which "seldom produce other than a very scanty crop of inferior and imperfect berries,"--and of males, which produce none. (7/8. Mr. Leonard Wray 'Gardener's Chronicle' 1861 page 716.) The most skilful cultivators plant "seven rows of female plants, then one row of hermaphrodites, and so on throughout the field." The males bear large, the hermaphrodites mid-sized, and the females small flowers. The latter plants produce few runners, whilst the two other forms produce many; consequently, as has been observed both in England and in the United States, the polleniferous forms increase rapidly and tend to supplant the females. We may therefore infer that much more vital force is expended in the production of ovules and fruit than in the production of pollen. Another species, the Hautbois strawberry (F. elatior), is more strictly dioecious; but Lindley made by selection an hermaphrodite stock. (7/9. For references and further information on this subject, see 'Variation under Domestication' chapter 10 2nd edition volume 1 page 375.)
Rhamnus catharticus (RHAMNEAE).
(FIGURE 7.13. Rhamnus catharticus (from Caspary.) Left: Long-styled male. Right: Short-styled male.)
(FIGURE 7.14. Rhamnus catharticus. Left: Long-styled female. Right: Short-styled female.)
This plant is well known to be dioecious. My son William found the two sexes growing in about equal numbers in the Isle of Wight, and sent me specimens, together with observations on them. Each sex consists of two sub-forms. The two forms of the male differ in their pistils: in some plants it is quite small, without any distinct stigma; in others the pistil is much more developed, with the papillae on the stigmatic surfaces moderately large. The ovules in both kinds of males are in an aborted condition. On my mentioning this case to Professor Caspary, he examined several male plants in the botanic gardens at Konigsberg, where there were no females, and sent me the drawings in Figure 7.13.
In the English plants the petals are not so greatly reduced as represented in this drawing. My son observed that those males which had their pistils moderately well-developed bore slightly larger flowers, and, what is very remarkable, their pollen-grains exceeded by a little in diameter those of the males with greatly reduced pistils. This fact is opposed to the belief that the present species was once heterostyled; for in this case it might have been expected that the shorter-styled plants would have had larger pollen-grains.
In the female plants the stamens are in an extremely rudimentary condition, much more so than the pistils in the males. The pistil varies considerably in length in the female plants, so that they may be divided into two sub-forms according to the length of this organ. Both the petals and sepals are decidedly smaller in the females than in the males; and the sepals do not turn downwards, as do those of the male flowers when mature. All the flowers on the same male or same female bush, though subject to some variability, belong to the same sub-form; and as my son never experienced any difficulty in deciding under which class a plant ought to be included, he believes that the two sub-forms of the same sex do not graduate into one another. I can form no satisfactory theory how the four forms of this plant originated.
Rhamnus lanceolatus.
This plant exists in the United States, as I am informed by Professor Asa Gray, under two hermaphrodite forms. In the one, which may be called the short-styled, the flowers are sub-solitary, and include a pistil about two-thirds or only half as long as that in the other form; it has also shorter stigmas. The stamens are of equal length in the two forms; but the anthers of the short-styled contain rather less pollen, as far as I could judge from a few dried flowers. My son compared the pollen-grains from the two forms, and those from the long-styled flowers were to those from the short-styled, on an average from ten measurements, as 10 to 9 in diameter; so that the two hermaphrodite forms of this species resemble in this respect the two male forms of R.