OCR Text |
Show 288 DICECIOUS AND CHAP. VII. those in the allied genus Celastrus are said to be "polygamo-direcious." If a number of bushes of our spindle-tree be examined, about half w~ll. be ~ound to have stamens equal in length to the pistil, with welldeveloped anthers ; the pistil being likewise to all appearance well developed. . ~he other hal~ have .a perfect pistil, with the stamens short, beanng rudimentary anthers destitute of pollen ; so that these bushes are females. All the flowers on the same plant present the same structure. The female corolla is smaller than that on the polleniferous bushes. The two forms are shown in the accompanying drawings. Fig. 12. Hermaphrodite or male. Female. EUONYMUS EUROP iEUS. I did not at first doubt that this species existed under an hermaphro9.ite and female form; but we shall presently see that some of the bushes which appear to be hermaphrodites never produce fruit, and these are in fact males. The species, therefore, is pol~gamous in the sense in which I use the term, an~ tnoicous. The flowers are frequented by many D1ptera and some small Hymenoptera for the sake o~ the nectar secreted by the disc, but I did not see a single bee at work ; nevertheless the other insects sufficed to CHAP. VII. POLYGAMOUS PLANTS. 289 fertilise effectually female bushes growing at a distance of even 30 yards from any polleniferous bush. The small anthers borne by the short stamens of the female flow~rs are well formed and dehisce pro .. perly, but I could never find in them a single grain of pollen. It is somewhat difficult to compare the length of the pistils in the two forms, as they vary somewhat in this respect and continue to grow after the anthers are mature. The pistils, therefore, in old flowers on a polleniferous plant are often of considerably greater length than in young flowers on a female plant. On this account the pistils from five flowers from so many hermaphrodite or male bushes were compared with those from five female bushes, before the anthers had dehisced and whilst the rudimentary ones were of a pink colour and not at all shrivelled. These two sets of pistils did not differ in length, or if there was any difference those of the polleniferous flowers were rather the longest. In one hermaphrodite plant, which produced during three years very few and poor fruit, the pistil much exceeded in length the stamens bearing perfect and as yet closed anthers; and I never saw such a case on any female plant. It is a surprising fact that the pistil in the male and in the semi-sterile hermaphrodite flowers has not been reduced in length, seeing ~hat it performs very poorly or not at all .its proper function. :he stigmas in the two forms are exactly alike ; and 1 U some of the polleniferous plants which never produce~ a~y fruit I found that the surface of the stigma was VIsmd, so that pollen-grains adhered to it and had ?Xserted their tubes. The ovules are of equal size ~n t~e two forms. Therefore the most acute botanist, Judging only by structure, would never have suspected u |