160 AN GIOSPERM A E DICOTYLEDON ES 



399. V. parviflora Moench (=S. Vaccaria Z.). (Herm. Mtiller, ' Weit. Beob.,' 

 II, pp. 231-2; Schulz, 'Beitrage,' II, pp. 23-4; Kirchner, 'Flora v. Stuttgart,' 

 p. 247.) This species bears butterfly flowers. Herm. Miiller says that the expansion 

 of the calyx is so great that its diameter below the middle may be as much as 7 mm. 

 Its ventricose surface is deeply enfolded between the sharp projecting longitudinal 

 ribs. The protection against robbery by humble-bees e.g. Bombus terrester 

 is thus rendered more effective, as the bees cannot perforate the folds, and if they 

 bite through the edges can scarcely reach the nectar. The folds also hold together 

 the claws of the petals, which are flesh-coloured to rose-red. The calyx-tube narrows 

 above, so that it is almost closed by the petals, stamens, and pistil, and can only 

 be traversed by the proboscis of a butterfly. Nectar is secreted in small quantities 

 at the bottom of the calyx, at a depth of 15-18 mm. The flowers are sometimes 

 slightly protogynous, not infrequently protandrous, and often homogamous. Auto- 

 matic self-pollination is always possible. Kerner says that it is brought about 

 by continued growth of the stamens. Although autogamy is indicated by the 

 inconspicuousness of the flowers, cross-pollination by insects is ensured at the 

 beginning of anthesis. Female flowers have been observed, in addition to the herma- 

 phrodite ones. The plant is gynomonoecious and gynodioecious. 



Visitors. Schulz observed butterflies in eastern Westphalia, i. e. species of 

 Pieris, especially P. brassicae Z. 



120. Cucubalus Tourn. 



The ventricose companulate calyx protects the flower from humble-bees; the 

 petals gradually narrow into the long claws. 



400. C. baccifer L. Schulz (' Beitrage,' II, p. 81) states that the hermaphrodite 

 flowers of this species are protandrous. There are also a small number of female 

 flowers on the same, or on special plants. 



121. Silene L. 



Protandrous, homogamous, or protogynous flowers, with nectar concealed in 

 various ways. The calyx is tubular to ventricose, serving in the latter case as 

 a protection against the bites of nectar-stealing humble-bees. A corona is sometimes 

 present. The long claws of the petals are often held together so firmly by the 

 calyx that the approach to the nectar secreted in the base of the flower is only 

 available to Lepidoptera ; many species of this genus, therefore, belong to the flower 

 class L. In other species the nectar is easily accessible to long-tongued bees, 

 and such species are placed in class H. There are also many flowers in which 

 the nectar is still less deeply concealed, and these belong to class C. One species 

 S. Otites is peculiar in being chiefly anemophilous. Gynomonoecism and gyno- 

 dioecism are common. 



According to Rohrbach ('Monogr. d. Gatt. Silene,' Leipzig, 1868, pp. 41-3), 

 the following species are exclusively autogamous : S. antirrhina Z., S. apetala Willd., 

 S. cerastoides Z., S. clandestina Jacq., S. gallica Z., S. hirsuta Lag., S. inaperta Z., 

 S. longicaulis Pourr., S. tridentata Desf. 



