. Botany of the living plant. Botany; Plants. APPENDIX A 651 A distal lobes. The syngenesious anthers form a dark purple tube, with a terminal beak. The style bears below the stigma-lobes a ring of bristles, which acts like a sweep's brush upon the pollen. The flowers are protandrous as before. The filaments are curved and sensi- tive, contracting on the stimulus of touch. This is received by hairs radiating out from them ; honey is secreted at the base of the corolla (Fig. 501). The insect visitors are most commonly bees. Inserting the proboscis into the tube of a floret with stigma not yet r
. Botany of the living plant. Botany; Plants. APPENDIX A 651 A distal lobes. The syngenesious anthers form a dark purple tube, with a terminal beak. The style bears below the stigma-lobes a ring of bristles, which acts like a sweep's brush upon the pollen. The flowers are protandrous as before. The filaments are curved and sensi- tive, contracting on the stimulus of touch. This is received by hairs radiating out from them ; honey is secreted at the base of the corolla (Fig. 501). The insect visitors are most commonly bees. Inserting the proboscis into the tube of a floret with stigma not yet receptive, the filaments are stimulated ; they straighten and contract, drawing the anther-tube downwards. The bristles of the style thus brush out the pollen at the moment the insect is there, and it is deposited on his body. If he then passes to a floret with stigmas expanded cross-pollination is ensured. But self-pollination is also possible by curva- ture of the stigmas to touch the pollen carried on the stylar brush. These examples show how differences of detail in the florets of the Tubuliflorae may be effective in pollination : the fundamental facts being a protandrous condition, and an aggregated - 6 B Fig. 501. Stamens and style of Centaurca- A, in the unstimulated, B, in the stimulated state. The style in the latter projects beyond the anthers, and the pollen has been brushed out. (After Strasburger.) (ii) Liguliflorae. (45) The Common Dandelion, or any Hawk-weed, will serve as an example. The Dandelion (Taraxacum officinale, Web.) is a perennial herb, with massive storage root, a rosette of radical leaves, and solitary, long-stalked heads. The tissues are traversed by branched latex-tubes containing milky-juice. The head consists of an involucre of bracts (Fig. 5°2» *), seated at the margin of a naked, pitted general receptacle (gr.). Within are numerous ligulatc florets, which are all alike, and have the same number and relation of parts as in the T
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