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V 



338 MR. G. BENTHAM ON THE MlMOSEzE. 



the testa, and remains so after soaking for days ; whilst the true albumen of Mimosa is 

 quite detached from the testa, and after soaking for a day or two resolves itself into a 

 transparent jelly. In Acacia Berteriana, which proves to be identical with my I*ithe- 

 colobitim fragrans, belonging to an exalbuminous group, I do find within the testa, on 

 each side of the embryo, a small quantity of an almost gelatinous . substance, the origin 

 of which remains to be ascertained. It is certainly different in many respects both from 



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the undoubted albumen of Mimosa, Leuccena, and their allies, and from the above-men- 

 tioned inner coatmg of Acacia farnesiana ; but whether it is an exudation from the inner 

 seed-coating, or a real albumen, as supposed by Schleiden, remains doubtful. I find no 

 trace of it in the seeds of the nearest aUied species, Pithecolohimn poly cepJialum . 



The universally acknowledged importance of carpological characters in the general 

 classification of phenogamous plants has induced the majority of botanists to rely mainly 

 upon them for the detailed subdivision of Mimosese, with results above alluded to as 

 being far from satisfactory. There are species of Fiptadenia, of AcacicB {Vulgares), and 

 of Albizziaj of which the pods can scarcely be distinguished from each other, whilst in 

 flowers and all other characters these Fiptadenim are much more nearly aUied to Ade- 

 nanthera or Eritada, the Acaclce (fulgares) to Acacice {GummifercB), and the AlUzzice 

 to Fithecolobium, all with very different fruits ; and the great diversities in the pods of 

 some of the most natural groups, such as Acacia {JPhyllodinecs), Acacia (Gummifera), 

 Inga, Mimosa, &c., may be seen by a glance at Plates LXVI. to LXX. The modifications 

 of the pod arc, indeed, rarely structural, more frequently limited to outward form, con- 

 sistency, or degree of dehiscence, characters resulting from diversity of development 



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enlargement as they approach Maturity, affording no indication at or immediately 

 after the period of fecundation ; as, however, in some instances the characters derivable 

 from the pod have acquired so great a degree of constancy as to be really available for 

 the separation of more or less natural groups, it may be useful to pass in review such of 

 these differences as have been, or may be, made use of with more or less of advantage. 



The consistency of the pod, that is of the pericarp, thin and papery, thicker and 

 coriaceous, woody, thick and spongy, or fleshy and succulent, has lost much of its sup- 

 posed value, as almost aU the varieties are observable in one or two species, at least, of 

 the natural and well-defined genus Acacia-, the fleshy or succulent pericarp upon which 

 the genus Inga was originally founded, entailed the including in it many species which 

 are more naturally distributed in. the genera Farkia, Strypknodetidron, Fithecolobium, 

 and even Acacia, and is by no means constant in Inga itself, the pod of several species 

 of the sections Leptinga and Bourgonia being apparently dry and coriaceous ; the 

 succulent pod, however, is nearly general in Inga, Farkia, and Stryplmodendron, pre- 



Fithecolobi 



very rare in Acacia, CalUandra, and Fiptadenia, and 



observed in Albizzla, Mimosa, Leuccena, or perhaps in any genus with albuminous seeds 

 except Stryphuodendron. 



With regard to dehiscence, or the sei^aration of the two valves at maturity, the 

 absolute difference between the dehiscent and nondehiscent species is not very defined. 

 Generally indehiscent in Inga, usuaUy, but by no means always, dehiscent in Acacia, 

 Fiptadenia^ and Albizzia, very variable in Fithecolobium, the pod is, I believe, always 



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