180 
Monopetale, and Polypetale. The first that we can find are, 
to use Dr. Carruthers’? words, ‘‘not generalised types, but 
differentiated forms, which, during the intervening epochs, 
have not developed even into higher generic groups.” 
To take, for instance, the Dakota group in North America, 
among its 130 species, as yet known, only one may. be doubt- 
fully referred to the Cycads; there are only five Cryptogams, 
six Conifers, and two Monocotyledons ; all the rest are Dico- 
tyledons, distributed into genera, much as now; of Apetale 
it has Amentacee, Myricacee, Platanee, Salicinee ; of 
Gamopetale, Bicornes, Hbenacee, &c.; of Polypetale, Mag- 
noliacee, Sapindacee, Menispermacee, &e. As Dr. Les- 
quereux says (Cretaceous Flora, p. 38),—“ it has represen- 
tatives of all the classes of plants, without disproportion, in 
one degree or the other, as compared to what is considered 
the scale of the vegetable kingdom. This seems to prove a 
collateral development of different primitive types, and, 
therefore, the appearance at certain epochs of those original 
forms which, at each geological period, have changed the 
character of the vegetable world, and which do not have any 
connexion with antecedent types.”? Again, still more de- 
cidedly (p. 35),. after remarking that it is easy to build up 
imaginary systems of derivation from supposed simple types, 
by mere deviations or multiplications of organs, he goes on:— 
“But until we know more we have to consider the facts. - 
“And the conclusion evidently forced, at least in considering 
the flora of the Dakota group, is that its disconnexion from 
ancient types is so wide that even the supposition of inter- 
mediate, unknown, extinct vegetable types fails to account 
for the origination of its peculiar characters.” 
So far as the evidence of the Upper Cretaceous Dicotyle- 
donous remains goes, it is decidedly opposed to the theory of 
descent. It is opposed to it in two ways. First, by the 
sudden emergence of the class already differentiated into sub- 
groups it irresistibly suggests some abrupt origin of that 
class, such as immediate creation. Secondly, by the proof of 
the persistence of generic types so complicated as that of the 
tulip-tree from that distant period to the present day without 
any apparent change, it negatives any theory which.is built 
upon the indefinite variability of systematic characters. 
8. The Flora of the Coal Measures—We now come to the 
most fascinating of all the extinct floras, that of the Palzeozoic 
Coal Measures. The imagination is wonderfully attracted by 
the picture which science calls up of these old-world forests. 
Stretching for hundreds of miles along the swampy margins 
of estuaries, and covering the surface of. their low deltas, they 
