121 



ice a thread-like proboscis may be thrust, notably the ants, who are not abroad 



but a creeping insect cannot pass. after "the dew falls." 



In the snapdragon the two lips of the Protection against grazing animals, 



flower are tightly closed, the lower one Although we are considering the ways 



decidedly projecting. Any small inject by which creeping insects are checked in 



reaching- this lower lip as a natural land- their efforts to visit flowers, it seems per- 



ing place finds no entrance. When the tinent to mention the more universal 



bumblebee alights upon the lower lip, danger which comes from grazing ani- 



how^ver, his weight depresses it and he mals. If flowers were as attractive to 



forces his way in, and in passing to an- grazing animals as they are to insects 



other flower effects pollination. It is in- they would be in danger of wholesale de- 



teresting to note that after this first and struction. It can be observed, however, 



important visit the lips remain open and that these animals as a rule avoid the 



other insects pass in freely, "being in- flowers of a plant, although they may 



vited," as some one has said, "to eat at strip off its leaves. It is believed that this 



the second table." avoidance is due to the fact that in or 



In most of the orchids there is a very about the flower cluster there are usually 

 complete adaptation of the flower to its secreted bitter, sour, or nauseous sub- 

 insect, by which almost every insect ex- stances, which grazing animals have 

 cepting one special kind obtains nothing learned to avoid. It should not be im- 

 for its visit. The nectar is usually in the agined that these substances are there for 

 end of a long spur, and to obtain it the that purpose, but being there the result 

 head of the insect must just fit between is that the flowers are avoided. It is un- 

 two sticky buttons to which the pollen- known how generally true this is, and the 

 masses are attached. The length of the effectiveness of this method of protection 

 spur is nicely adjusted to the length of may have been exaggerated. Those who 

 the proboscis of the visiting insect, but can observe cattle, however, are in a posi- 

 his head must also be of a certain breadth, tion to test them with the flowers of the 

 If an insect visits the flower with a pro- various plants they are known to eat, and 

 boscis too short or too long, or a head determine how far they avoid them, 

 too broad or too narrow, its visit is un- In conclusion, it may be of interest to 

 availing. The danger of such narrow call attention to the great complexity of 

 specialization is apparent in the case of relations existing among plants and ani- 

 the orchids, for each plant is so depen- mals by repeating Darwin's famous illus- 

 dent upon a special insect that the dis- tration known as "Cats and Clover." In 

 appearance of the latter seriously en- a certain district in England he observed 

 dangers the continued existence of the that the clover was pollinated by the bum- 

 former, blebees, which had their nests in the 



Protective closure. It has long been fields. It followed, therefore, that the 



noticed that certain flowers open only in more the bumblebees, the more the 



the evening, the evening primrose being clover. He also observed that the field 



a conspicuous example. These flowers mice preyed upon the young broods of 



are adapted to the visits of the night- the bumblebees, and, therefore, the more 



fliers, the moths, and about clusters of the field mice, the fewer the bumblebees 



evening primroses numerous large hawk- and the less the clover. When cats were 



moths may be seen after sunset. During plenty and preyed upon the field mice it 



the day the flowers are closed and safe followed that the more the cats, the fewer 



from the visits of any insect, but by open- the mice, the more the bumblebees, and 



ing in the evening they are not only ready the more the clover. Therefore, the crop 



for the visits of the night-fliers, but they f clover depended upon the presence of 



avoid the visits of most creeping insects, cat s in the neighborhood. 



John Merle Coulter. 



