PROTECTION OF POLLEN. 115 



en reserved for another destiny which we shall have to consider more 

 refully later on. In any case the pollen adherent to the projecting end of the 

 i^le, near the mouth of the tube composed of the connate anthers, must be 

 otected before nightfall, when there will be condensation of dew, or in case of 

 Lq being imminent. This protection is, in fact, afforded to each floret by the 

 ;ule of the adjoining corolla, which stretches out laterally and constitutes an 

 abrella. In the Hawkweeds (Hieracium) the ligule bends so as to form a 

 vering over the pollen to be protected (cf. figs. 222 ^ and 222^). In Catananche, 

 other Composite, each ligule is spread out flat whilst the sun shines, but in 

 e evening becomes concave and at the same time arches over the pollen belonging 

 its own flower (fig. 222*). We cannot here go into all the diflerences in detail 

 aich occur in connection with this form of adaptation. We must not, however, 

 erlook the fact that in these Composites the ligules of the peripheral florets of a 

 pitulum are always much longer than those of the central florets, and that the 

 illen of the latter shares therefore the protection from wet aflbrded by the 

 nding over of the outer ligules. We do not mean to say that the short ligules 

 the middle of the capitulum are not required to take any part at all in sheltering 

 e pollen. In most instances they, too, stand up and curve over inwards, and 

 t in conjunction with the longer outer ones in preventing the entrance of water, 

 le adaptation of the flowers of Catananche is carried so far that the long ligules 



the peripheral florets cease to bend inwards when there is no longer any pollen 



protect in those florets — that is to say, when the pollen has been brushed ofl" 

 d the florets have entered into their last stage of development (cf. fig. 222^). 

 le short ligulate florets in the central part of the capitulum must then of course 

 B to the protection of their pollen themselves. This is the reason why one sees 

 ly the central ligules of old heads of Catananche arched inwards, whilst those 

 ar the margin remain motionless and stand out in rays during the dewy night 

 st as they do under the noontide sun. 



The mechanism for the protection of the pollen is well worthy of notice in 

 ose Composites also in which the central florets of the capitula are all tubular 

 d the peripheral florets all ligulate, and in those where the tubular florets are 

 3wded together on a round disc and encompassed by an involucre of stiff leaves 

 lich resemble petals. The Marigold (Calendula) may be taken as type of the 

 st group, and the Carline Thistle (Carlina acaulis) as type of the second 

 g. 224). In these plants the style grows and pushes the pollen out at the top 



the tubular florets, just as in the case of the ligulate flowers above described 

 was pushed up through the hollow cylinder formed by the connate anthers, 

 d above each floret a little lump of pollen is seen resting upon the free end of 

 B style. These tubular florets are, however, incapable of securing their pollen 

 ainst bad weather, and a division of labour is therefore in some degree instituted 

 thin the limits of each capitulum, the ligulate florets or radiating marginal 

 lets, as the case may be, which produce no pollen, being turned to account 

 • the purpose of sheltering the pollen-bearing florets of the centre. In fine 



