. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. COMPOSITAE 66i 478. Cnicus L. Style of the hermaphrodite florets very similar to that of Centaurea (montana). 1565. C. benedictus L. (Hildebrand, 'U. d. Geschlechtsverhalt. b. d. Com- positen,' pp. 57-8, Taf. V, Fig. 31.)—Although the anthers appear normal in this species, the first florets produce no pollen. The neuter ray-florets are so small as to be hardly visible beside the disk-florets. 479. Centaurea L. Ray-florets neuter, tubular, radiating. Disk-flo
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. COMPOSITAE 66i 478. Cnicus L. Style of the hermaphrodite florets very similar to that of Centaurea (montana). 1565. C. benedictus L. (Hildebrand, 'U. d. Geschlechtsverhalt. b. d. Com- positen,' pp. 57-8, Taf. V, Fig. 31.)—Although the anthers appear normal in this species, the first florets produce no pollen. The neuter ray-florets are so small as to be hardly visible beside the disk-florets. 479. Centaurea L. Ray-florets neuter, tubular, radiating. Disk-florets hermaphrodite. Filaments very irritable. Below the short broad stylar branches a ring of sweeping-hairs directed obliquely upwards; above this short hairs on the style ; stig- matic papillae on the inner sur- faces of the branches. Kemer states that the pollen is concealed in the anther-cylinder until insects visit the florets, being thus pro- tected from rain and dew. When the proboscis of a nectar-seeking insect stimulates the filaments, they contract so that the crumbling pollen is carried off by the visitor as soon as it is swept out. After removal of the pollen, only cross- fertilization is possible for a short time; the stylar branches then roll back in such a way that the stigmatic papillae touch the pollen still clinging to the sweeping-hairs, thus effecting self-pollination. I have not myself observed this rolling back of the branches. In some species—C. aipina (Wett- stein); C. montana, in the Apen- nines (Delpino), but not at Vienna (Wettstein)—nectar is secreted by the involucral bracts of the bud, as in Serratula lycopifolia, S. cen- iauroides,andJurineamollis. Wett- stein observed the ant Campo- notus sylvaticus Oliv., var. aethiops Latz., on C. aipina in Istria, 1566. C. Jacea L. (Herm. Muller, ' Fertilisation,' pp. 346-9, ' Weit. Beob.,' Ill, pp. 79-80, ' Alpenblumen,' p. 415; Loew, 'Bliitenbiol. Floristik,' pp. 390, 393, 397 ; MacLeod, Bot. Jaarb. Do
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