82 DIGITALIS PtUPUREA. CHAP. III. 



the larger humble-bees, which, whilst in search of nectar, carry 

 pollen from flower to flower. The two upper and longer 

 stamens shed their pollen before the two lower and shorter 

 ones. The meaning of this fact probably is, as Dr. Ogle re- 

 marks,* that the anthers of the longer stamens stand near to 

 the stigma, so that they would be the most likely to fertilise it ; 

 and as it is an advantage to avoid self-fertilisation, they shed 

 their pollen first, thus lessening the chance. There is, however, 

 but little danger of self-fertilisation until the bifid stigma 

 opens ; for Hildebrand f found that pollen placed on the stigma 

 before it had opened produced no effect. The anthers, which 

 are large, stand at first transversely with respect to the tubular 

 corolla, and if they were to dehisce in this position they would, 

 as Dr. Ogle also remarks, smear with pollen the whole back and 

 sides of an entering humble-bee in a useless manner ; but the 

 anthers twist round and place themselves longitudinally before 

 they dehisce. The lower and inner side of the mouth of the 

 corolla is thickly clothed with hairs, and these collect so much 

 of the fallen pollen that I have seen the under surface of a 

 humble-bee thickly dusted with it ; but this can never be ap- 

 plied to the stigma, as the bees in retreating do not turn their 

 under surfaces upwards. I was therefore puzzled whether these 

 . hairs were of any use ; but Mr. Belt has, I think, explained 

 their use : the smaller kinds of bees are not fitted to fertilise 

 the flowers, and if they were allowed to enter easily they would 

 steal much nectar, and fewer large bees would haunt the 

 flowers. Humble-bees can crawl into the dependent flowers 

 with the greatest ease, using the "hairs as footholds while 

 sucking the honey ; but the smaller bees are impeded by 

 them, and when, having at length struggled through them, they 

 reach the slippery precipice above, they are completely 

 baffled." Mr. Belt says that he watched many flowers during 

 a whole season in North Wales, and " only once saw a small 

 bee reach the nectary, though many were seen trying in vain to 

 doso."* 



I covered a plant growing in its native soil in North Wales 

 with a net, and fertilised six flowers each with its own pollen, 



* 'Popular Science Review,' gua,' 1874, p. 132. But it appears 



Jan. 1870, p. 50. from H. Miiller (' Die Befruchtung 



t Geschlechter - Vertheilung der Blumen,' 1873, p. 285), that 



boi den Pflanzen,' 1867, p. 20. small insects sometimes succeed 



J ' The Naturalist in Nicara- in entering the flowers. 



