" DIPSACE^ 229 



We have two species, or forms — D. sylvestris, with 

 ovoid heads, and very prickly ; and D. pilosus, with 

 globular heads, and very hairy. 



D. sylvestris. — One of the stigmas is generally 

 atrophied. H. Miiller suggests that as the tube of the 

 corolla is narrow, if both stigmas were retained there 

 would be no room for the proboscis of the bee, and that 

 fertilisation being secured, a second stigma is un- 

 necessary. The leaves are sessile and broadly connate 

 at the base, forming a water-collecting cup round the 

 stem, which effectually prevents creeping insects from 

 reaching the flowers. The water thus collected is also 

 probably useful as aS"ording the plant a supply in dry 

 weather. The Fuller's Teazel, in which the scales of 

 the receptacle terminate in hooks, is sometimes regarded 

 as a variety of D. sylvestris, sometimes as a separate 

 specieSj D. Fullonum. 



SCABIOSA 



We have three species. One, S. succisa, has entire 

 leaves. In the other two the leaves are divided ; one, 

 S. Columbaria, has the florets five-lobed, the other, S. 

 arvensis, four-lobed. 



S. arvensis. — When the flower opens the stamens 

 project 4-5 mm. above the corolla, and the anthers open 

 one after the other, so that this stage lasts several days. 

 When they have all shed their pollen they shrink up. 

 The pistil now elongates, and the ripe stigmas take up 

 the position previously occupied by the anthers. The 

 florets open from the circumference towards the centre, 

 but the central florets have all shed their pollen before 

 the stigmas of the outer ones are ripe ; so that not only 

 each floret, but the whole head, is at first male, and sub- 

 sequently female. Self-fertilisation is therefore excluded ; 

 but this is immaterial as the flowers are so richly visited 

 by insects — something over 100 species are recorded. 

 Some plants also have female flowers, especially early in 

 the season. In Kent, Darwin found the female flowers 

 much less numerous than the others. According to 



