82 



FOSSIL PLANTS. 



mode de developpement que cette famille partage avec les Foiigeres, et probablement 

 avec qiielqiies autres families voisines, et qui devrait faire reserver a ce groupe de 

 vegetaux le nom tres-juste d'Acrogenes, applique par M. Lindley a toutes les Cryptogames 

 et Agames." 



This no doubt is true with regard to Lycopodiacea ; but with respect to Lejndodendron, 

 Halonia, and Sigillaria, the two first-named genera exhibiting no traces of medullary 

 rays, whilst the latter possesses them, are very like Acrogens ; but most assuredly the last- 

 named genus, and probably the other two, were exogenous plants, as the specimens 

 formerly described by me distinctly prove/ 



V. Bibliographical History of Halonia. 



Having thus concluded my description of the internal structure of the stem of 

 Lepidodendron and its mode of dichotomization, I will now proceed to describe some 

 specimens of Halonia regularis. First, however, it is desirable to give a short sketch of 

 the present state of our knowledge of this fossil plant. 



Several authors have distinctly stated that Lepidodendron had roots resembling 

 those of Stigmaria ; and Mr. Dawes, who possessed in 1848 by far the most perfect 

 specimens then known, hinted that Halonia might prove to be the root of Lepidodendron. 



§ L Lindley and Hutton. 



a. " Halonia ? tortuosa} — In sandstone in a quarry near South Shields, from a 

 specimen furnished by Isaac Cookson, Esq. 



" Whatever this may have been, it is evidently very distinct from anything hitherto 

 described. Probably the present specimen has been jammed and distorted so much as to 

 have lost, in a great measure, its original character ; but enough remains to convey some 

 idea of its external structure. 



" It seems to have been a plant of small dimensions, the surface of whose stem was 

 completely covered with little processes, which, in falling away, left minute quincuncial 

 ill-defined spots, that rapidly became separated and obliterated as the stem advanced in 

 age. Among these spots, at intervals of three fourths of an inch every way, were 

 arranged little projections, the apex of which was terminated by some appendage now 

 lost. The ramification appears to have been dichotomous, but this is extremely 

 uncertain. 



1 ' Quart. Journ. Geol. Soc' for May, 1862, vol. xviii; and ' Phil. Trans.,' volume for 1865, p. 576. 



2 Lindley and Hutton's 'Fossil Flora,' vol. ii, p. 85, 1833—5. 



