FERTILIZATION OF SPRING FLOWERS ON THE YORKSHIRE COAST. 185 



leaves should be — to justify this departure from the usual state of 

 things — a successful organism. Besides, the flowering of the 

 simpler plants often is spread over a very considerable time, but 

 in the coltsfoot the flowering season is for the most part compressed 

 into one month. 



On the cliffs over the sea, where this plant abounds, the capitula 

 contain about 200-300 ? florets, and about 40 3 . On the slopes 

 of the moors, at heights of 400-500 ft. above the sea, the capitula 

 are usually smaller, sometimes as little as 15 ram. in diameter, 

 those on the clifls being 20-3G mm. With the less size of capitulum 

 the number of disc florets is much reduced, and at the same time 

 the tube of the flowers is shorter (3 mm. and upwards, those from 

 the chfl's being 5-6 mm.), so that the less conspicuous the in- 

 florescence is, the more accessible is the honey. 



Daring flowering the tube of each disc-flower grows upwards of 

 1 mm. ; at the same time the ligulate florets are growing, and also 

 the receptacle is broadening. Thus the whole capitulum becomes 

 somewhat more conspicuous as it i)asses over from the early stage, 

 where none but $ florets are mature, to the late S stage. As the 

 capitulum becomes old and the growth of the corollas ceases, the 

 power of closing at night, which, as is well known, depends on 

 the unequal growth in the ligules of the ligulate florets, is gradually 

 lost. In consequence, the ? flowers are better protected than the 

 (? from the inclemencies of the weather. The bracts of the involucre 

 ill no way help in the expanding of the capitulum, but by main- 

 taining a constant steady pressure tend rather to retard it. 



The relation of ? to c? flowers is interesting, and bears out the 

 well-marked specialization of the order. In most plants the fertili- 

 zation of the ovules is the signal for the withering of the corolla of 

 that flower : it is not so here, for the ? flowers may all be fertilized 

 before any 3^ floret is open and yet maintain their freshness, upon 

 which the conspicuousness of the capitulum depends, until the last 

 S flower has shed its pollen. Neutral florets with contabescent 

 anthers may occasionally be found among the disc-florets. 



The flower-season of the plant was almost completely observed; 

 and we may compare the species of insect-visitors observed with 

 those given by other observers, without the suspicion that perhaps 

 the ditierences are due to want of observation of the whole of the 

 plant's period of bloom. 



Again, one remarks the greater proportions of the lower insects 

 in Britain than in Germany. Miiller observed Apis visiting "in 



H. Miiller, Aliitnhlumeii, p. ioo; Leipzig, 1881. 



