ALLIES OF THE PLANT WORLD 
and useful guests come to their nectar-feasts. 
The very Ants which guard the lower portions 
of a plant so well, might become mere greedy 
plunderers, if allowed to crawl within the 
flowers. It is not often that they do. Some- 
times, the stalks and even the petals of flowers 
like the Rock-Lichens and the Butter-Wort are 
coated with some plant chemical exceedingly 
disagreeable for an insect to crawl over. Various 
alkaloids, resins and oils in the cell juices also 
make the flower and its leaves obnoxious to 
grazing animals. Many plants, like the Mul- 
lein and Stinging-Nettle, use bristles and 
prickles to repel Slugs and Caterpillars. 
A common protective device is for a flower 
to place its nectar at the bottom of a long, nar- 
row tube only accessible to a flying insect hav- 
ing a proboscis. In the Antirrhinum the en- 
trance to the flower is closed to small crawlers 
by a very heavy corolla. Bees, because of their 
size and strength, can force their way through. 
It is said that as soon as the stigma of this flower 
has been fertilized, the corolla relaxes and Ants 
and their kind are free to enter and partake of 
such dainties as are left. 
[75] 
