amare, Cunninghamie and Arancarie, are mixed (according to episto- 
latory communications from Dr. Debeg), several most peculiar extinet 
genera; the Dicotyledons Bikey as is well known, appear first in the Cre- 
Seeainn formatio n, present t emselves in the lower chalk only in few, 
(namely in Credneria and gh gals but in the chalk of Aix, in 
humerous species. According to the communications from Dr. Debe 
to whom we owe an excellent work on these pants (cf. die urwelilichen 
Thallophyten und Acrobryen, Denkschriften der Wicner-Academie, xvi, 
and xvii), he has discovered in Aix about 200 species of Dicotyledons. 
= 
taccous] yeas in my opinion to Tees He Gat ya. This flora o 
Aix shows, therefore, a Ae ided Indio-Australian character, 
proaches thereby the Eocene flor ora, while that of the older Chalk hiitok 
is foreshadowing the URE to that of the Jura. How different the flora 
of Nebraska oe having all the now known genera in common with 
the Miocene flo: all the hag ho generic types met in Amer- 
ica at the present pri If it y belongs to the oldest Chalk forma- 
tion, the flora of that epoch Paes shu aly itself to the present flora of 
Ameri ica, and there faa | Gndging by the small amount of oat ig since 
that time not occurred any new arrangement which had materially 
changed the genera, while this was the case in Europe’ in a high “dees, 
Many peculiar forms join the older ie rie ee in the lower Chalk, and 
the Dicotyledons appear mostly in now extinct genera; after this the flora 
assumes more and more the TeaieA peas vie tet, which continues 
through the Pliocene flora to the commencement of the Miocene; then 
the In 8 igre types retreat by degrees into + background, making 
room for merican, this prevailing to the end of the Miocene epoch, 
and, in pir species, reaching i into Pieces while in the Quaternary 
epoch the Asiatic types make their apipdaritnds with the present creation, 
predetermining the character of the vegetation. No doubt it is possible, 
that the American flora has assumed from the Cretaceous period an en- 
tirely different development from that of Europe; but ere we accept such 
a remarkable phenomenon as a fact, we had rather wait for further exam- 
inations of the localities where the Nebraska oe are found. I must 
about the co 
urope. How easily accessible are our Alps in comparison to the parts 
of America in question, and how long a time did it take, before we on 
correctly informed on the rela tions ot the strata of the most oo 
Saeed and how much are we in the dark yet about some of 
those very mountains! It is now generally admitted, that with us oe 
tovidstioas are resting on Tertiary for an extent of over 36 miles. “Ther 
* They ca Feiss Sid to to Oytisus, because the secondary veins project too much; 
they “ur however, t racter of walnut -leaves. 
Am. Jour. rhage ont Serres, Vi ‘oL. XXXI, No. 93.—May, 1861. 
57 
