65 



A summary 



of 



the morphology and biology of the Ericineœ. 



All the Ericineæ are adapted for cross-pollination by 

 insects, and some instances are known of the visits of insects 

 (mostly species of humble bees) to the flowers, although these 

 visits appear to occur very sparsely and rarely. All the species 

 here in question, with the exception of Pirola, secrete honey. 

 The honey-secreting organs surround the base of the ovary, or 

 in the case of superior flowers, the base of the style. As many 

 of the species have drooping flowers it is evidently a useful 

 feature that several have hairs near the base of the filaments 

 and of the petals which serve to retain the honey and to pre- 

 vent intruders from entering. This is doubtless also the reason 

 why the base of the filaments is swollen in some of the species 

 {Rhododendron, Ledum, Cassiope hypnoides, Andromeda poli- 

 folia, Ärctostaphylos, PhyUodoce). 



All the flowers are coloured, the majority are even of a 

 conspicuous colour. Some of them are scented [Ledum, Pirola, 

 Cassiope tefragona, С hypnoides, Ar do staphylo s alpina, Vacci- 

 nium uliginosum, and (according to Bessels) PhyUodoce). 



The pollen grains which, as is well-known, are always united 

 into tetrads, are quite glabrous and dry; even before the buds 

 open the pores at the apex of the anthers are generally formed, 

 and the grains lie loosely in the air-filled pollen-sacs, even if 

 they are not always dry enough to fall out easily. This is 

 also the case in Denmark with Erica Tetralix and Calliina vul- 

 garis. Exceptions to this are Loiseletiria, the anthers of which 

 are of the usual kind, and PhyUodoce. 



The sole function of the appendages, which occur on the 

 anthers of all the species which have bell-shaped and drooping 

 xxxvi. 5 



