67 



extreme narrowness of the throat: the hairs serve to gather up 

 the pollen grains as they fall and to retain them until they either 

 are conveyed by chance to the proboscis of an insect-visitor, 

 or fall upon the stigma of the same flower. No species in 

 which the corolla has a wide mouth has such hairs, because 

 in such a case they would be superfluous. When they are 

 wanting also in other species which have narrow throats {Vac- 

 cinium Mijrtillus, Lyonia and Phyllodoce to which may be 

 added Erica Tetralix and Erica cinerea) the reason may per- 

 haps be found in the fact that the pores of the anthers are so 

 near to the mouth of the flower that there would be difficulty 

 in spreading the pollen in the interior of the corolla. 



The stigma has in all the species only very small papillae, 

 but secretes mucilage abundantly which, in specimens preserved 

 in spirit, appears hardened and usually filled with small vacuole- 

 like balls. The stigma always reaches at least the level of the 

 anthers, but usually it is higher than they and will therefore 

 easily and immediately be able to receive the pollen which may 

 have been brought by an insect-visitor. 



On the other hand, self-pollination will in most cases be 

 able to take place easily, as the stigma lies below the anthers, 

 either on account of the position of the flower — in the greater 

 number of species the mouth of the flower turns downwards — 

 or else because the style is bent downwards , as in Pirola, 

 and must inevitably in this position be dusted with the pollen 

 when it is shed. And with regard to this point, there occurs 

 in some Arctic species, as already shewn, a tendency to facilitate 

 self-pollination, the distance between the pores and the stigma 

 being shortened, and the chances of a favourable result being 

 thereby made greater. But in regard to this, Pirola rotundi- 

 folia f. grandifiora differs from the typical form ; Vaccinium 

 Vitis-idœa f. pumilum from the typical species; and the Phyl- 

 lodoce specimens among themselves. In Loiseleuria the anthers 

 also appear to approach nearer to the stigma than they do in 



