114 . INTRODUCTION 
5. Social Flowers with completely concealed Nectar (S). 
Nectar is here concealed as in the preceding class, but the flowers are united 
into heads, so that they are not only rendered strikingly conspicuous, but there 
is also a possibility of several flowers being simultaneously pollinated. To this 
Fic. 23. Flowers of Group CH. (1) Rubus saxatilis Z. (in outline). (2) Vaccinium Vitis- 
Idaea Z. (in outline). (3) Polemonium caeruleum ZL. 
group belong Compositae (except the anemophilous genus Artemisia). Here also 
are included species of the genera Knautia, Scabiosa, Succisa, and Armeria. 
Fic. 24. Soctal Flowers. (1).Chrysanthemum alpinum Z. (2) Gnaphalium 
Leontopodium Scop. 
Social flowers fall into two sharply demarcated oecological groups: wz%es and 
yellows on the one hand, where the insect visitors are akin to those of flowers with 
partly concealed nectar (which are almost always of these colours), and reds, blues. 
