92 ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
so situated that insects creeping up the stem are sure to find it. 
As soon as the Balsam begins to open its flowers nectar is abun- 
dantly secreted by these nectaries, and being both abundant and 
more accessible than that in the flowers, unwelcome guests are 
diverted from these. Regarding this sweet fluid and its use Kerner 
makes the following remarks:—“ The honey-loving ants lick it up 
eagerly, and are content not to 
stray farther upwards. Actual 
observation shows that the 
flowers of J/mpatiens tricorntis 
are free from ants, whilst these 
stipular nectaries are much fre- 
quented by them. Their pres- 
ence in. the flowers is very un- 
desirable, since they could readily 
get at the honey there without 
touching the pollen or stigma. 
And more than this, they would 
not only pilfer the honey, but 
they would also drive away those 
winged insects for which the 
honey is prepared—the welcome 
guests that pollinate the flowers. 
We are justified on the facts in 
regarding this diversion of the 
unbidden guests as an indirect 
protection of the floral honey.” 
Insects are not infrequently 
prevented from reaching the 
flowers by means of a watery 
barrier. This is obviously so in 
the case of water-lilies and other aquatic plants, and may also be 
observed in some land forms. In Teasels, for example, the leaves 
are arranged in pairs, the bases of each pair being united together 
to form a sort of cup, in which water collects, so as completely to 
surround the stem (fig. 1082). 
Slippery surfaces are often present, on which creeping insects 
can find no foothold. There is sometimes a smooth coating of 
wax, as in certain Willows, where the catkin-bearing twigs are 
thus protected. Another interesting case is that of the Snowdrop 
Fig. 1082.—A Teasel (Dzpsacus laciniatus), showing 
water-cups formed by fusion of bases of leaves 
