94 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
brushes and thickets of hairs are present, guarding the entrance 
and rendering access difficult, whilst still allowing it. Large 
and powerful animals find these obstacles no hindrance, and 
readily brush them aside; small ones, however, cannot do this, 
but have to climb over or circumvent the obstacles. And in 
many cases this enforced divergence by small insects from the 
direct path brings about the desired result. For, in circumventing 
these folds and barricades and hairs, they are unconsciously led 
past the anthers and stigmas, contact with which is unavoidable. 
Thus, what would otherwise be useless visitants become welcome 
guests. They are conducted indirectly 
to the honey by these curious struc- 
tures, which may, in a sense, be termed 
‘path-finders’.” Cursory examination 
of such flowers as Foxglove or Pansy 
will show the presence of barricades 
of the kind mentioned (see also fig. 
1085). Path-finders for the guidance 
of invited guests are often present in 
the form of conspicuous colour-streaks, 
which converge towards the source 
Fig. 1085.—Section through Flower of a Of nectar. Pansy, Azalea, and Pelar- 
prontie taht of hair eaiea "= = Gonium are particularly good examples 
of this. 
The defences and other arrangements which have been evolved 
in various connections by plants and animals are never completely 
successful, and with changed surroundings are apt to fail. This 
applies not only to ‘mice and men”, but also to flowers. Kerner 
states, for example, that the flowers of some 300 European plants 
are systematically robbed by humble-bees, which take a short cut 
to the nectar by biting through the calyx or corolla. The result 
may be disastrous, for in some of these plants but few seeds are 
produced, so that they are becoming rare, and in course of time 
will probably die out altogether. Certain Alpine Catch-Flies (Szdene 
Pumito and S. Efizabethe) are in this evil case. Kerner suggests 
that such plants date back to a time when there were no, or but 
few, humble-bees in the region where they now grow, and that they 
have since failed to evolve means of defence against the new kind 
of attack. 
Wingless enemies of soft-bodied character, especially snails 
