172 BRITISH PLANTS 
into three classes, based upon the availability of the 
honey : 
1. Those with freely-exposed honey, which may be 
visited by all kinds of insects, even those with the shortest — 
tongues (flies, beetles, short-tongued bees, wasps)—e.g., 
saxifrages, galium, ivy, most of the Umbellifere, bar- 
berry, hedge- mustard, spindle-tree. Many of these 
flowers are small, but their conspicuousness is increased 
by the massing of them together (see paragraph on in- 
florescences, p. 178), or they make their presence evident 
by a strong scent. Short-tongued insects are not efficient 
pollinators, because they seldom confine their attention 
to one species of flower. Such flowers are also more 
Fic. 72.—Curistmas Rose (Helleborus). 
1, longitudinal section of flower: a, honey-leaf; b, carpels ; c, stamens ; 
d, sepals ; e, receptacle. 2, honey-leaf, enlarged. 
exposed than others to insects which rob them of honey, 
but are useless in effecting pollination. They are also 
liable to have their honey spoiled by rain. 
2. Flowers with half-concealed honey. These are, 
evolutionally, flowers of a higher type than Class 1. 
Their honey lies deeper, and is more difficult to get at. 
It is more protected from rain, and is less exposed to the 
ravages of unwelcome guests—e.g., buttercup, stonecrop, 
many Crucifers, potentil, etc. There is every gradation 
between the flowers of this class and the preceding. The 
insects have tongues between 2 and 3 lines long (a line 
is js inch). They are mostly short-tongued bees and 
the longer-tongued flies. Among the unbidden guests of 
flowers are the wingless and crawling insects—e.g., ants. 
They enter the flower on foot, but before the honey is 
reached the path is often stopped by viscid secretions on 
