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II. " On the Structure and Affinities of Trigonocarpon (a fossil 

 fruit of the Coal-measures)." By JOSEPH D. HOOKER, 

 M.D., F.R.S. Received March 23, 1854. 



Having been for some time engaged in examining the structure 

 and affinities of some fossil fruits of the coal formation, included 

 under the name Trigonocarpon, and the progress which I am enabled 

 to make being extremely slow (owing to the difficulty of procuring 

 good specimens), I am induced to lay before the Royal Society such 

 results as I have arrived at, for publication in their Proceedings (if 

 thought worthy of that honour). The details and illustrations of 

 the subject will, when complete, be offered to the Geological Society 

 of London. 



My attention has for many years been directed to the genus Tri- 

 gonocarpon ; as, from the period of my earliest acquaintance with 

 the flora of the carboniferous epoch, I have felt assured, that bota- 

 nically, this was the most interesting and important fossil which it 

 contained in any great abundance, and that until the affinities of this 

 were determined, the real nature of the flora in question could never 

 be regarded as even approximately ascertained. 



In the first place, Trigonocarpon is so abundant throughout the 

 coal-measures, that in certain localities some species may be pro- 

 cured by the bushel ; nor is there any part of the formation in which 

 they do not occur, except the underclays and limestone. The sand- 

 stone, ironstones, shales and coal itself, all contain them. 



Secondly. The symmetry in form and size which many of them 

 display, the regularity of the sculpturing on their surfaces, and 

 various other points, suggested their belonging to a class of highly 

 organized vegetables. 



Thirdly. The fact of our being wholly unacquainted with the 

 organs of fructification belonging to the exogenous vegetation, which 

 also abounds in the coal formation, coupled with the assumed highly 

 organized nature of Trigonocarpon, favoured the assumption that 

 these might throw light upon one another, and seemed to afford a 

 legitimate basis upon which to proceed, should I ever procure speci- 

 mens of Trigonocarpon displaying structure, which I had long hoped 

 to do. 



