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Show 292 DHECIOUS AND CHAP. VII. year, or during the two previous years, produce a single fruit. If these latter bushes and the more fertile female ones were to supplant the others, the spindle-tree would be as strictly dioocious in function as any plant in the world. This case appears to me very interesting, as showing how gradually an hermaphrodite plant 1nay be converted into a dioocious one.* Seeing how general it is for organs which are almost or quite functionless to be reduced in size, it is remarkable that the pistils of the polleniferous plants should equal or even exceed in length those of the highly fertile female plants. This fact fonnerly led me to suppose that the spindle-tree had once been heterostyled; the hermaphrodite and n1ale plants having been originally long-styled, with the pistils Rince reduced. in length, but with the stamens retaining their fonner dimensions; whilst the female plant had been originally short-sty led, with the pistil in its present state, but with the stamens since greatly reduced and rendered rudimentary. A conversion of this kind is at least possible, although it is the reverse of that which appears actually to have occurred with some Rubiaceous genera and .lEgiphila; for with these plants the short-styled form has beco1ne the male, and the long-styled the fe1nale. It is, however, a more 8imple view that sufficient time has not elapsed for the * According to Fritz Muller ('Bot. Zeitung,' 1870, p. 151), a Chamissoa (Amaranthacere) in Southern Brazil is in nearly the same state as our Euonymus. 'l'he ovules are equally developed in the two forms. In the female the pistil is perfect, whilst the anthers are entirely de~titute of pollen. In the polleniferous form, the pistil ia short and the stigmas never separate from on: ano.ther, ~0 that, altlJOugh theu surfaces are covered with fairly well-~ev~l?pcd papillro, they cannot be fertilised. These latter plants u.o not cu~monly yield any frmt. and are therefore in function males. N ev~rtheless, on one occa::,i~n .Fn~ Miillerfoundflowersofthls Innd ~ which the stigmas had s~pa.rate ' and thoy produced some frmt. CHAP. VII. POLYGAMOUS PLANTS. 293 reduction of the pistil in the male and hermaphrodite flowers of our Euonymus ; though this view does not account for the pistils in the polleniferous flowers being sometimes longer than those in the female flowers. Fragaria vesca, Virginiana, Ohiloensis, &e. (Rosacem ). -A tendency to the separation of the sexes in the cultivated strawberry see1ns to be much more strongly marked in the United States than in Europe; and this appears to be the result of the direct action of climate on the reproductive organs. 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 i1nperfect berries," -anq of males, which produce none. 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 ?oth 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 sp~cies, t?e Hautbois strawberry (J/. elatior), is more stnctly d1oocious; but Lindley made by selAction an hermaphrodite stock. t Rhamnus catharticus (Rhamnere ).-This plant is well * 1\fr. Leonard "Vray in 'Gard. Chron.' 1861, p. 716. t For references and further infor~a~ion on this subject, see ' Vanatwn under Domestication ' chap. x. 2ml edit. vol. i. p. 375. ' |