xxiv PROOFS, ILLUSTRATIONS, AUTHORITIES, ETC. 



Leucisci, Tenches, Loaches, Gudgeons, etc., but neither Trouts nor 

 Salmon." Bib. Univ. de Geneve, No. 100, Article on Agassizs 

 Becherches. 



9. THERE IS A SUCCESSION FROM LOW TO HIGH TYPES 

 IN FOSSIL PLANTS, FROM THE EARLIEST STRATA IN 

 WHICH THEY ARE FOUND, TO THE HIGHEST. 



On fossil plants the highest authority is M. Adolphe Brongniart. 

 He has presented to the Institute his tinal views " on the Chrono- 

 logical Exposition of the Periods of Vegetation and the different 

 Floras which have succeeded each other on the Earth's Surface." 

 In this paper, he remarks " the predominance, in the most ancient 

 periods, of acrogenous-cryptogamous vegetables (Ferns and Lyco- 

 podiacea) ; later, the predominance of gymnospermous dicotyledons 

 (Cycadeoe and coniferee), without any mixture hitherto of angiosper- 

 mous dicotyledons; and in the last place, during the chalk forma- 

 tion, the appearance and speedy predominance of angiospermous 

 vegetables, both dicotyledons and monocotyledons." 



In the first period, which he calls the Reign of Acrogens, gymno- 

 sperms, a superior type, come in (sigillarits, naeygeratkice, and aste- 

 ropliylliteai] ; but the sigillarise would appear to predominate in the 

 middle and superior beds, and the asterophyllites, and particularly 

 the annularia, are found much more abundantly in the superior 

 beds : " it is the same with the Coniferce, and it is only in the supe- 

 rior beds of St. Etienne, Autun, etc., that branches have been found, 

 at least in France." 



"The gymnosperms," he elsewhere says, "show themselves in 

 unusual forms, and sometimes so anomalous, that we are in doubt 

 whether to place them in this or the preceding department [that of 

 acrogenous cryptogams] ; such are the asterophj'llitese." 



M. Brongniart holds as doubtful most of the alleged instances of 

 plants of the carboniferous era found below the zone of the coal 

 formation. One carboniferous formation in the neighbourhood of 

 Oporto, which appears of very ancient date, since it is covered by 

 beds containing fossil animals characteristic of the Silurian formation, 

 contains some impressions of plants, and these impressions all of 

 ferns (thus exclusively Acrogens). 



The Flora of the carboniferous period contains, according to M. 

 Brongniart, only about 500 well-determined species of plants, scarcely 

 a twentieth part of the number now flourishing on the face of the 

 globe. " This number of species, moreover, corresponds to a long 

 period during which diverse species succeeded each other, so that we 

 may admit with much probability that never more than 100 species 

 existed simultaneously. We thus perceive what was the poverty and 

 especially the uniformity of this vegetation. 



" Does this vegetation, thus reduced to the forms which we are led 



