KNAPWEED 



59 



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

 times enlarged and neuter as in Centaurea Cyamis. 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 (Centaurea 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 w 7 ill reveal two kinds of cluster cup, 

 Puccinia arenariicola and P. centaurcce. A gall, Chiophora solstitialis, 

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

 moths Parasia metznerinella, Coleophora conspiciella, C. alcyonipennella, 

 Common Heath (Fidonia atomaria], Lime Speck (Eupithecia centau- 

 reata, Depressaria liturella, D. arenella; a Heteropterous insect, Onco- 

 tylus viridiflavus; and the flies Urcllis data, U. /[-fasciata, Trypeta 

 jacetz. 



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



