ON THE STUDY OF ADAPTATION IN PLANTS. 179 



place. Besides these, however, there are further adapta- 

 tions to be taken into consideration which concern the 

 characters of the organs and tissues, as well as those which 

 result in the exhibition of irritability, or in responsive action 

 to a stimulus. 



In both cases a study of adaptations has often led to 

 erroneous conclusions. For in order to understand them 

 aright we must possess precise and accurate knowledge on 

 two distinct subjects. First, the conditions of life of the 

 plant ; this alone, however, will not suffice, there must be 

 at our disposal, secondly, the results of investigations on the 

 comparative morphology of kindred plants, a side of the 

 question to which I shall revert below. 



Among the social adaptations the ant-plants have 

 attracted special attention. 1 Thomas Belt deserves the 

 merit of having first recognised that ants play an 

 important part in the lives of some South American 

 plants, which are constantly inhabited by those insects. I 

 refer to certain species of Cecropia, characterised by their 

 hollow and remarkably constructed internodes, in which 

 the ants live, attracted and retained there by the food- 

 bodies which are situated at the basis of the leaves ; there 

 are also some Acacia whose hollow thorns are inhabited 

 by ants, and food is provided for them at the expense of 

 the plant. Belt's statement that the ants sheltered by these 

 plants serve the latter as a protecting army against the 

 devastations of the leaf-cutting ants has been fully con- 

 firmed. And the number of plants which either harboured 

 ants, or attracted them by extra floral nectarias, has been 



1 Belt, The Naturalist in Nicaragua, 2nd edition, London, 1886. Among 

 other works on ant-plants I should quote : Beccari, Piante ospitatrici della 

 Malesia e della Papuasia in Malesia, ii., 1886. Delpino, Funzione myrme- 

 cofila nel regno vegetale, iii. theile, Bologna, 1886- 1889. Treub, Sur le 

 Myrmecodia de Java, Annates du jardin. hot. d. Buitenzorg, vol. vii. 

 Bower, On Hutnboldtia laurifolia as a myrmecophelous plant, Proc. Phil. 

 Soc. Glasgow, xviii. Schumann, Einige neue Ameisen pflanzen, Pringsheims 

 Jahrb., xix. Schumann, Ueber africanische Ameisen pflanzen, Per. der 

 deutschen botan. Gesellschaft, 1891, heft ii. Wettstein, in Sitz. Per. der 

 Wiener Akad. math.-naturw. Ciasse, xcvii. bd., p. 568. 



