68 BRITISH FLOWERING VLANTS chap. 



flowers of this kind it is, of course, obvious that insects 

 will dust themselves with the pollen and then carry it 

 with them to other flowers. In Berberis, however, 

 both advantages, the dusting and the cross-fertilisation, 

 are promoted by a very curious contrivance. The 

 bases of the stamens are highly irri- 

 table, and when an insect touches them 

 the stamens spring forward to the 

 position shown in Fig. 40 and strike 

 the insect. The eff'ect of this is not 

 only to shed the pollen over the in- 

 sect, but also in some cases to startle 

 Fia. i^.-BerUris-ovi- -^ ^ ^ | '^ go ^^^^ ^f; carrics 



(jans. Pistil and two •' . -, 



stamens, after the the poUcn thus acquircd to another 



Muchfnia^gec'""' ^owcr. It is visitcd by bccs, wasps, 



flies, and beetles. 



The fruits show the characteristic features of those 



adapted for dissemination of the seeds by serving as 



food for animals! The fruits themselves are juicy and 



red, with a pleasant taste. In other cases they are 



generally sweet, but in the Berberry have a pleasant 



bitter taste. The seeds have a hardened endosperm 



and a crustaceous testa, so that they are'not digested. 



The Berberry had long been suspected by farmers 

 of exercising an injurious influence on wheat, and they 

 generally therefore rooted it out of hedges; The sus- 

 picion, however, was regarded as groundless, until it 

 Avas found that the plant (Puccinia graminis) to 

 which "rust" is due passes through two phases: in 

 one it lives on wheat, in the other on the Berberry, 

 The second phase had been regarded as a distinct 

 fungus, JEcidium herberidis ; it forms yellowish-brown 

 pustules on the leaves and young shoots in the early 

 summer. 



