RELATIONS Ol ; ANTS TO I'ASCULAR PLANTS. 



3 11 



cessible to the ants throve as well as those filled with the insects. 

 And he, Karsten, Rettig and others, after a careful study, found that 

 the walls of the cavities are provided with lenticelli and that the cavi- 

 ties themselves probably have a twofold function: to contain air and 

 thus prevent the tissues of the plant from becoming overheated during 

 hot, dry spells, and to take up and to store water for purposes of 

 growth at other seasons of the year. It would seem, therefore, that 

 the ants merely take advantage of the cavities without either bene- 

 fiting or injuring the plant. 



This case oiMyrmecodia and the allied Rubiaceas is very interesting 

 as epitomizing the change of opinion which will eventually extend to 

 other instances of so- 



called symbiosis between 

 ants and plants. Rum- 

 phius in 1750 declared 

 Myrmccodia to be a zoo- 

 phyte, believing that the 

 ants brought together 

 twigs and built a nest 

 out of which the Myr- 

 mecodia germinated. He 

 therefore called the 

 plant " nidus germinans 

 fonnicaruin rubraruin ct 

 nigrarum." Now we 

 have a physiological ex- 

 planation, which some 

 may regard as a sordid 

 anticlimax to this and 

 other fanciful views 

 concerning the relations 

 of the Myrmecodia to 

 its tenants. But to the 

 thinking naturalist Rum- 

 phius's explanation is 

 merely a childish absurdity, while that of the recent botanists is 

 infinitely more stimulating to the scientific imagination, disclosing as 

 it does, on the one hand, the age-long struggles of a plant to live on the 

 atmosphere and its moisture while exposed on hot cliffs and tree- 

 trunks, and, on the other hand, the no less persistent endeavors of the 

 plastic ant to find new domiciles for its pullulating commonwealths. 

 The classical account of the relations of Acacia sphcerocephala ( Fig. 



FIG. 179. Ant gardens of the Amazon. (Ule.) 

 A, Large spherical ant garden covered with seed- 

 ling plants ; B . small garden on Cordia. 



