AUTOGAMY IN CLEISTOGAMIC FLOWERS. 393 



-clandestina, a widely-distributed bog-grass allied to the Rice-plant. The panicles 

 of this Oryza include chiefly flowers which remain closed and are adapted to 

 .autogamy; they develop only on their very highest branches a few flowers which 

 open and may be cross-pollinated by the agency of the wind. On the other hand, 

 the number of species possessing cleistogamous flowers to be found amongst plants 

 ■with adhesive pollen, and liable to be crossed by insect agency, is very large. 

 Numbers of tropical and sub- tropical Asclepiadaceae, Malpighiacese, Papilionaceae, and 

 Orchidacese afford instructive examples of this phenomenon. The splendid colours 

 of the open flowers in these plants attract insects, and if the flowers are visited 

 cross -pollination is rendered inevitable by the various kinds of apparatus for 

 pressing, sprinkling, or shooting the pollen upon the insects with which the flowers 

 are furnished; but if in spite of allurements no insects arrive, the stigmas are not 

 besmeared with pollen at all, and these great open flowers wither without forming 

 fruit. It then comes to the turn of the cleistogamous flowers. They are developed 

 in the axils of special leaves as small, greenish, bud -like structures, which are 

 destitute of means for alluring insects, but are none the less sure on this account to 

 produce ripe fruit and fertile seeds. There is, besides, in temperate zones, no lack 

 of plants in which the same phenomenon may be observed. A host of Bell-flowers, 

 Rock-roses, Balsams, Polygalacefje, Oxalidaceee, and Scrophulariacese (e.g. Cam- 

 panula, Specularia, HelianthemuTn, Impatiens, Polygala, Oxalis, Linaria) and, in 

 particular, the Violas of the dominium and Dischidium, sections, exhibit the same 

 .difference in the functions assigned to their two kinds of flowers. The beautiful 

 Viola mirahilis has scented flowers stored with honey, which unfold great violet 

 petals in the spring. If these blossoms are visited by hive- or humble-bees they 

 a,re cross-fertilized; but many are not thus visited, and their fate is then to wither 

 without effecting that process of autogamy which has been described (p. 387) as 

 taking place in the species of Violet belonging to the Melaniwm section. In the 

 summer, however, special branches of the same individual plant bring forth small 

 green flower -buds which do not open, but nevertheless produce soon afterwards 

 large ripe capsules full of seeds. This phenomenon, in apparent contradiction to 

 the ordinary idea of the result of the flowering process, did not escape the attention 

 of the Botanists of the eighteenth century, and they named this species of Violet, in 

 which the majority of the large open blossoms fail to produce fruit whilst the closed 

 bud-like flowers are invariably productive, Viola mirahilis, or the Wonderful Violet. 

 In Viola mirabilis and in all its allied species, called "caulescent" in the 

 language of descriptive Botany, the cleistogamous flowers are developed on special 

 shoots, and these shoots are either erect or else prostrate in long zigzags. This is 

 also the case in several species of. the Wood-sorrel genus (Oxalis) and in Aremonia 

 agrimonioides, A few Papilionaceae (e.g. Vicia amphicarpa) and Cruciferse (e.g. 

 Gardam,ine chenopodiifolia) are known too, whose cleistogamous flowers spring 

 from underground runners or stalks, whilst the open flowers are borne upon aerial 

 shoots. In several Violets of the kind called by descriptive Botanists " acaulescent", 

 such as Viola collina and V. sepincola, the cleistogamous flowers develop likewise 



