[Illustration: Fig. 72.--Cineraria. (Magnified.)] Another point for attaining this end is worthy of remark. The outer ring of florets is distinguished by long, coloured petals, which make up, in common parlance, the flower of the cineraria. These serve to render the composite head conspicuous, and attractive to insects. Some varieties, moreover, emit fragrant odours, and thus present further inducements for visitation. It is remarkable that, in these florets of the outer edge, the gay-coloured petals are developed at the expense of the anthers. Consequently, they produce no pollen, and their pistils have no brushes, as there would be no office for them to perform. The bright rays have accomplished their own special purpose, and the florets may well depend on others for pollen. Now, as to the great importance of cross-fertilisation in this species, we may quote the experiments made by Dr. Darwin.[11] He says: "Two purple-flowered varieties (of cineraria) were placed under a net in the greenhouse, and four corymbs (or bunches of flowers) on each were repeatedly brushed with flowers from the other plant, so that their stigmas were well covered with each other's pollen. Two of the eight corymbs thus treated produced very few seeds, but the other six produced on an average 41.3 seeds per corymb, and these germinated well. The stigmas on four other corymbs on both plants were well smeared with pollen from the flowers on their own corymbs; these eight corymbs produced altogether ten extremely poor seeds, which proved incapable of germinating. I examined many flowers on both plants, and found the stigmas spontaneously covered with pollen; but they produced not a single seed. These plants were afterwards left uncovered in the same house, where many other cinerarias were in flower; and the flowers were frequently visited by bees. They then produced plenty of seed, but one of the two plants less than the other, as this species shows some tendency to be diœcious. [Footnote 11: See _Cross and Self-Fertilisation of Plants_, p. 335.] "The trial was repeated on another variety with white petals tipped with red. Many stigmas on two corymbs were covered with pollen from the foregoing purple variety, and these produced eleven and twenty-two seeds, which germinated well. A large number of the stigmas on several of the other corymbs were repeatedly smeared with pollen from their own corymb; but they yielded only five very poor seeds, which were incapable of germination. Therefore the above three plants, belonging to two varieties, though growing vigorously and fertile with pollen from either of the other two plants, were utterly sterile with pollen from other flowers on the same plant." [Illustration: Fig. 73.--Tropœolum Majus. (Young bloom.)] [Illustration: Fig. 74.--Tropœolum Majus. (Old bloom.)]