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342 



MR. G. BENTHAM ON THE MIMOSE^ 



bush/ varying in degree of development 



the 



al pairs of stipules of the same 



branch, but affecting special forms and tinges of colour, from an ivory-white to a livid 

 purple, for each species. They are generally hollow, with a small opening in one horn of 

 each pair leading to the cavity, which is continuous throughout, and, in America at 

 least, are usually, like the swellings at the base of the leaves of some South American 

 Melastomacese, in the stems of some South American Labiatae, or Malayan Eubiacese, 

 &c., tenanted by colonies of stinging ants, much to the annoyance of collectors. Por 

 careful observations as well as for speculations on the supposed relation of these abnormal 

 developments to the preservation of the species as well as to the welfare of their tenants, 

 I may refer to Belt's 



most 



interesting ' Naturalist in Nicaragua,' p. 218 



I am not 



J- 



of any special attention having been paid to them in the Indian peninsula 



Arabia, or North-east Africa, where these product 



abound: nor 



we informed 



1 



even whether they are there, as in America, occupied by ants. I know of no instance 

 where any similar enlargement takes place in the spinescent stipules of the Australian 



L ■ 



Acacice of the I^hyllodinecB or of the 'Pulcliellce groups, nor in those o^ F if hecolobium, 

 section Zfnguis-cati, or of CalUandra colletloides, C. geminata, &c. Very much, there- 



-■ - r 



^^ ^^ I 



fore,, has yet to be observed before we can be said to be well acquainted with the history 



of these product 



all that can 



be stated generally is, that they appear to be 



the combined result of hereditary constitution, of soil and climate, and of the working 

 of ants. What share each cause has had in the general effect remains to be as- 

 certained. 



The geographical dispersion of the more essential differences in character, such as the 

 limited and indefinite number of stamens, the glanduliferous and eglandular anthers, the 

 agglomeration and freedom of the pollen-grains, the albuminous and exalbuminous seeds, 

 and even the succulent and dry, as well as the articulate and inarticulate pods, would 

 ttmd to confirm that conclusion of the antiquity of these differences which we might 

 derive from the consideration of their systematic importance, i. e. of their stability and 

 definitcness ; and that antiquity must have been remote enough for the differentiation 

 to have taken place during a period previous to the geographical disruption of the race 

 of Mimoseae consequent on the change from a former to the present physical and 



geological configuration of the earth's surface 



Por of all the above pairs of distinctive 



characters both types have been developed in the Old World as well as in the Am 



forms, and not very differently 



We only observe generally that definite stamens 



albuminous seeds, and succulent articulate and indehiscent pods have been more favoured 

 in the New than in the Old World, and are unknown in races of Australian birth 

 except in a very few belonging to the north-eastern region and forming part of the 

 Indo-Australian rather than of the strictly . Australian flora ; whilst the Old- World 

 developments have been chiefly in the direction of the characters more or less specially 

 distinctive of or connected with the genus Acacia, 



TJpon the principles commented upon in the foregoing notes, the Mimoseae are con- 

 veniently divided for systematic purposes into the 29 genera, forming 3 tribes, as detailed 

 m the latter portion of the present paper ; but in considering, as I shall now proceed to 

 do, their genealogy and geographical distribution, more natural grades of subordination 



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