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flowers except Lyonia, Phyllodoce, and Vaccinium Vitis-idœa, 

 must be to serve as an aid in cross-pollination; the insect 

 will touch them and thereby shake the anthers so that the 

 pollen falls out. The fact that in the same species either the 

 anthers, or the appendages, or both these organs are covered 

 with small protuberances, must have the same purpose, viz. to 

 oppose the proboscis of the insect, and thereby increase the 

 resulting shock. That these appendages are, on the other hand, 

 wanting in species with open flowers which are usually more 

 or less erect or are, at most, horizontally projecting but not 

 drooping [Pirola, Loiseleuria, Ledum, Rhododendron), may easily 

 be understood. Vaccinium Oxycoccos also belongs to those 

 species in which the appendages are wanting, but its filaments 

 are covered with hairs which perhaps serve the same end. 

 This may apply also to Vaccinium Vitis-idœa. 



The fact that in many species the base of the filament is 

 very slender compared with the part just above it, appears also 

 to be useful ; it is thereby much easier for the insects to put 

 the filament in motion and shake it, than if its base had been 

 thick. 



Arctostaphylos cdpina occupies a peculiar position by 

 reason of the fact that its appendages are short, thick and 

 glabrous or even entirely wanting (aborted). This should be 

 correlated with the fact that the throat is very narrow, narrower 

 than in A. Uva-ursi, so that the insect must inevitably touch 

 the filaments and shed the pollen. This is also the case in 

 Phyllodoce. On comparing the above two species it will be 

 seen that while A. alpina is far the better adapted for self- 

 pollination, A. Uva-ursi is the better adapted for pollination 

 by insects. In the structure of its flower Andromeda polifolia 

 approaches nearest to Arctostaphylos Uva-ursi, especially in 

 that the interior of its corolla is covered with erect hairs as is 

 the case in the two species of Arctostaphylos. We may be 

 justified in concluding that these hairs are connected with the 



