126 



ZOOLOGY 



between animals and plants than among animals. The most 

 interesting of these latter are seen in the so-called "ant-loving" 

 plants, in which the plant produces special homes or special 

 foods used by the ants, and the ants in return protect the plant 

 from the ravages of other leaf-cutting ants or hurtful insects. 



Fig. 58. 



Fig. s8. Argynnis cyhele on thistle. Natural size. Photo by Folsom. 



Questions on the figure. — For what end does the butter-fly visit the thistle? 

 What special adaptations does the butter- fly possess for this mode of life? What 

 is the gain to the thistle from the visits? 



Certain sea-anemones possess unicellular algae imbedded in the 

 cells of the entoderm. These alg« derive their nourishment 

 from the wastes of the animal tissues and supply oxygen and 

 possible other matter to the cells in which they lie. The close 

 relation between the structure and instincts of insects, on the 

 one hand, and the form of flowers, their products and needs, on 

 the other, illustrates a symbiotic adaptation which has long 

 attracted students both of botany and zoology. See Fig. 58. 



161. Library studies. — -Make a report concerning the various myrmecophilous 

 plants. Accumulate all the supposed instances of symbiosis which your library 

 records. Lichens, among plants, are considered to illustrate symbiosis. How? 



