154 THE GEOLOGICAL HISTORY OF PLANTvS. 



Taxinece. There are numerous species, as well as allied seeds re- 

 ferred to the provisional genera Rhabdoearpvs and Carpolithes. 

 In Trigonocarpum HooJceri I have described the internal structure 

 of one of those seeds, and many fine examples from the coal-field of 

 St. Btienne, in France, have been described by Brongniart, so that 

 their internal structure is very well known. 



Genus Antholithes. 

 This is also a provisional genus, to include spikes of floral 

 organs, some of which are known to have belonged to Cordaites, 

 others probably to Sigillarice. 



Of Uncertain Affinities. 

 Faimily Sigillamacea 

 Under this name palsobotanists have included a great number 

 of trees of the Carboniferous system, all of which are characterised 

 by broad leaf -sears, witli three vascular scars, and usually arranged 

 in vertical rows, and by elongated three-nerved leaves, and roots of 

 the stigmaria type — that is, with rounded pits, marking the attach- 

 ment of rootlets spirally arranged. These trees, however, collected 

 in the genus Sigillaria by arbitrary characters, which pass into 

 those of the Lepidodendroid trees, have been involved in almost inex- 

 tricable confusion, to disentangle which it will be necessary to con- 

 sider : 1. The external characters of Sigillarim, and trees confounded 

 with them. 3. Subdivision of Sigillarias by external markings. 3. 

 The microscopic character of their stems. 4. What is known of 

 their foliage and fruit. 



1. Characters of Sigillaroid a/nd Lepidodendroid Tnmhs. 



It may be premised that the modes of determination in fossil 

 botany are necessarily different from those employed in recent bot- 

 any. The palseobotanist must have recourse to characters derived 

 from the leaves, the scars left by their fall, and the internal struct- 

 ures of the stem. These parts, held in little esteem by botanists in 

 describing modem plants, and much neglected by them, must hold 

 the first place in the regard of the fossil botanist, whereas the fructi- 

 fication, seldom preserved, and generally obscure, is of compara- 

 tively little service. It is to be remarked also that in such general- 

 ised plants as those of the Palaeozoic, remarkable rather for the de- 

 velopment of the vegetative than of the reproductive organs, the 

 former rise in importance as compared with their value in the study 

 of modem plants. 



