346 AUTOGAMY 



hooks; in the open llower they are straight and slope outwards. Contact with the 

 central stigmas, which meanwhile have become mature, is impossible so long as the 

 stamens maintain the latter position ; but shortly before the flower fades, the stamens 

 become inflexed, and their anthers are thus brought against the stigmas. The 

 Saxifrages also have two circles of stamens in each flower. In the species of the 

 sub -genus Cymbalaria (Saxifraga Cymbalaria, S. Huetiana, &c.), the first to 

 straighten out are those standing opposite the sepals. Their anthers open and 

 display their pollen at a time when the adjacent stigmas are closed together, and 

 are not as yet capable of taking up pollen. This supply of pollen is not therefore 

 used for autogamy, but is obviously available for crossing with other flowers. 

 After exposing their pollen one after another in definite order for a couple of days, 

 these stamens incline outwards and let their anthers fall. The styles, now, for the 

 first time, move asunder, and their stigmas become capable of receiving pollen. As 

 the anthers of the stamens opposite the sepals have dropped ofl', and those of the 

 stamens opposite the petals are still closed, the stigmas are only liable at this stage 

 in the development of the flower to be dusted with pollen from other flowers or 

 other plants. Eventually signs of vitality are also exhibited by the stamens 

 opposite the petals. They become strongly inflexed, their anthers dehisce, and, the 

 stigmas being still receptive, the period of the flower's duration is brought to a close 

 by the anthers being pressed against the stigmatic surface and efiecting autogamy. 

 The same sort of thing is observed in the case of the protandrous flowers of several 

 species of the genus Cuphea, as, for instance, in Ciiphea eminens. These flowers, 

 of which mention has already been made on p. 235 (figured on p. 237), face sideways 

 and contain eleven stamens of varying length whose anthers are disposed in two 

 irregular rows above the expanded calyx-tube. The style is short at the commence- 

 ment of flowering, and is concealed, together with the immature stigma, underneath 

 the anthers. Dehiscence occurs on the upper faces of the anthers which are turned 

 away from the style, and the pollen issuing from the sutures is fated by its position 

 to be rubbed off" by honey-sucking insects, and to be eventually used for cross- 

 fertilization. Two days later the style, which has in the meantime increased in 

 length some 11 mm., projects above the stamens, bringing the stigma into the line 

 of entrance to the honey (fig. 262 ^, p. 237). Should insects now visit the flower, 

 bringing with them foreign pollen, cross-fertilization is certain to ensue. But, in 

 the event of an absence of insects, the longest stamen bends up to the stigma and 

 presses that face of the anther which is coated with pollen against the stigma. 



The degree of inflection of the filaments in the cases hitherto described scarcely 

 corresponds to the third of the circumference of a circle, and is but seldom actually 

 spiral. But that more pronounced movements of inflection do occur for the purpose 

 of effecting autogamy, is shown by the case of Nicandra, a plant belonging to the 

 Solanacese, and that of Calandrinia compressa, belonging to the order Portulacese. 

 In Nicandra the long filaments bend down to the extent of at least a semicircle 

 to reach the stigma in the event of a failure of pollen from extraneous sources, and 

 in the ephemeral flowers of Calandrinia compressa, the filiform filaments curve 



