516 Royal Society. 



In the first place, Trlgonocarpon is so abundant throughout the 

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

 cured by the bushel ; nor is there any pai't 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 IjeJonging 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 Trlgonocarpon, 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 Trlgonocarpon displaying structure, which I had long hoped 

 to do. 



It is, however, only since my return from India that I have been so 

 fortunate as to obtain good specimens, and for these I am indebted 

 to my friend Mr. Binney of Manchester, who has himself thrown 

 much light upon tlie vegetation of the coal epoch, and whose exer- 

 tions indeed have alone enabled me to prosecute the subject ; since 

 he has not only placed his whole collection of Trigonocarpons at my 

 disposal, but has shared with me the trouble and expense of their 

 preparation for study. All the specimens were found imbedded in 

 a very tough and } ard black-band or clay ironstone, full of frag- 

 ments of vegetable matter, and which appears originally to have 

 been a fine tenacious clay. 



The individual Trigonocarpons are exposed by breaking this rock, 

 and are invariably so intimately adherent to the matrix as to be 

 fractured with it. A great manj' of these lumps of ironstone, con- 

 taining partially exposed Trigonocarpons, have been sliced by a lapi- 

 dary in the usual manner, and excessively thin sections taken on 

 slips of glass. The sections were made necessarily very much at 

 random, but as nearly as possible parallel, or at right angles to the 

 long diameter of the fruit. Five of the specimens thus operated 

 upon have proved instructive, presenting the same appearances, and 

 all being intelligible, and referable to one highly developed type of 

 plants. As, however, the term highly developed may ajjpear ambi- 

 guous, especially with reference to a higher or lower degree in the 

 scale of vegetable life, I maj' mention that by this term I mean to 

 imply that there are in the fruit of Trlgonocarpon extensive modifi- 

 cations of elementary organs, for the purpose of their adaptation to 

 special functions, and that these modifications are as great, and the 

 adaptation as special, as any to be found amongst analogous fruits 

 in the existing vegetable world. 



Thus, I find that the integuments of the fruit of Trlgofiocarpon are 

 each of them a special highly organized structure ; they are modifica- 

 tions of the several coats of one ovule, and indeed of the same num- 

 ber of integuments as now prevail in the ovules of living plants. 



