KNAPWEED 



59 



The marginal florets are like those in the centre, but are some- 

 times enlarged and neuter as in CcntaiLrea Cyanus. The corolla is 

 tubular, and enlarged above, making it accessible to many insects. 

 The flowerheads are purple and conspicuous. The central florets 

 are bisexual, the filaments glandular, and the anthers have an appen- 

 dage at the farther extremity. 



KNAPWEED (Centaitrea nigra, L.) 



The fruits have short hairs which aid in their dispersal by the wind 

 like other Composites. 



Knapweed is a clay plant, growing on clay soil, or sandy loam, 

 and is common on Triassic and Liassic formations, Boulder clay, &c. 



A search over the leaves will reveal two kinds of cluster cup, 

 Pnccinia arenariicola and P. centaurctz. A gall, Chiophora solstitialis, 

 infests it; two beetles, Spliaeroderma cardui, Cassida vibex\ the 

 moths Parasia victzncriiiella, Colcophora conspiciella, C. alcyonipennella, 

 Common Heath (Fidonia atoniaria\ Lime Speck (Eupithecia centau- 

 reata, Depressaria lit ure Ha, D. arenella; a Heteropterous insect, Onco- 

 tylus viridiflavus; and the flies Urcllis elata, U. ^.-fasciata, Trypcta 

 jacecc. 



Ceiitaurca, Pliny, is from Centaur, which is fabled to have had 



