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 Myrtillus, 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 papilla, 
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-visilor. 
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. grandiflora differs from the typical form; Vaccinium 
Vitis-idæa 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 
5* 
