57o AN GIOSPERM AE DICOTYLEDON ES 



surrounded in the bud by an involucre, usually made up of several series of 

 bracts. This subsequently serves as an adequate protection against creeping 

 animals, as well as to hold the inflorescence together. The whole is rendered 

 conspicuous by the crowding of the flowers, the effect being heightened by 

 outward curving of all the corollas, or by the production of the limb of each 

 into a long outer lobe. Finally, as in most cases, the marginal flowers have 

 lost their stamens, and even their pistils as well, being converted into long 

 radiating tongues that greatly add to the size of the head. These ray-florets 

 are often of a different colour from the disk-florets, so as to still further increase 

 the conspicuousness of the inflorescences. In a few cases (Carlina) the inner 

 bracts assume this function. 



Another result of crowding is that numerous flowers of the same inflorescence 

 are simultaneously pollinated by insects creeping over them in search of nectar, or 

 collecting or devouring pollen. For in the first stage of anthesis the pollen-grains, 

 in the second stage the stigmatic papillae, are so far above the general level that 

 insects must rub against them. It is thus highly probable that crossing will be 

 effected; but in many cases automatic self-pollination takes place in the absence 

 of insect visitors, for the branches of the style bend back, applying to the stigmatic 

 papillae pollen still clinging to the sweeping hairs. 



Nectar is secreted by a ridge surrounding the base of the style. It is so 

 abundant as to rise in the corolla-tube, and is protected from rain by the filaments 

 which converge above it. It is accessible both to long-tongued and short-tongued 

 insects. The Compositae are therefore typical examples of flower class S. 



In the markedly protandrous hermaphrodite flowers pollen is discharged even in 

 the bud into the anther-cylinder that surrounds the style with its apposed stigmas. 

 As the style elongates it sweeps the pollen before it out of the cylinder, so that the 

 grains accumulate above the opening of the flower. This is effected with the help of 

 hairs or papillae which beset the surface of the style, and which have a characteristic 

 form and arrangement in different genera. {Cf. Fig. 189.) Pollen adheres to 

 the ventral surface of insect visitors, this being rendered the more certain 

 because the filaments contract when touched by the proboscis as it is thrust 

 towards the nectar, so that the anther-tube often sinks several millimetres, and 

 the contained pollen is pressed out. After this has been accomplished the 

 stylar branches diverge, and the stigmatic papillae, which usually stud their inner 

 surfaces, become receptive. 



Another advantageous peculiarity of the Compositae, remarked by Sprengel, 

 is that the heads close in unfavourable weather. 



A short account (taken from Kerner, 'Nat. Hist. PI.,' Eng. Ed. 1, II, p. 318) 

 has already been given of the geitonogamy common in Compositae (Vol. I, pp. 41-2). 

 (Also cf. Fig. 191.) 



A. Tubuliflorae Less. 

 Disk-florets not ligulate. 



1. Sub-order Corymbiferae Juss. 

 Florets either all tubular or, more commonly, ray-florets ligulate. Style not 

 thickened at the tip, and devoid of a terminal circlet of sweeping hairs. 





