384 Mr. L. F. Ward on Mesozoic Dicotyledons. 
gained the ascendant as to dwarf all other forms into relative 
insignificance. ‘They include nearly all the deciduous forest 
trees, the shrubby undergrowth, the leafy herbage, and the 
weeds of all temperate regions. 
But this has not always been the case. In fact the reign 
of the Dicotyledons, geologically considered, has been very 
brief. Although there is evidence that the earth has been 
covered with vegetation since the beginning of the Carboni- 
ferous age at least, still there is nothing to warrant us in 
saying that a single dicotyledonous plant existed prior to the 
close of the Jurassic. Indeed, we do not know from the 
actual discovery of specimens that this type appeared earlier 
than the second recognized group of the Cretaceous—the 
Urgonian. Until quite recently the presence of these plants 
in formations lower than the Miocene was so rare that it was 
with the Tertiary rather than with the Cretaceous that the 
existing dominant vegetation of the globe was assumed to 
have originated. 
Notwithstanding this, some of the earliest, if not the very 
earliest, discoveries of these forms were in Cretaceous strata. 
In the stone-quarries of the Harz Mountains near Blanken- 
burg, were found, near the beginning of the eighteenth cen- 
tury, prints of large leaves which the workmen believed to 
be those of the grape-vine, and which were mentioned by 
Scheuchzer, Briickmann, and Walch, but without any attempt 
at their scientific determination. 
A brief historical review of the discovery, identification, 
and publication of dicotyledonous species in Cretaceous strata 
of Europe and America, including the arctic regions, will 
show the importance which this subject is assuming among 
alzontologists. 
In 1833 Zenker* took up in earnest the study of the Blank- 
enburg leaf-prints, and described, figured, and named five 
species belonging to two genera. One of these genera he 
rightly concluded to have no living representatives, and he 
therefore named it Credneria, after his friend Prof. Credner, 
who collected the specimens. 
In 1841 Goppertt figured a number of dicotyledonous leaves 
from the Quadersandstein of Silesia, but did not venture to 
give names to them. 
* ¢Beitrige zur Naturgeschichte der Urwelt,’ von Jonathan Carl Zenker, 
Jena, 1833. 
+ ‘ Ueber die fossile Flora der Quadersandsteinformation in Schlesien,’ 
c.,in Nova Acta Acad. Nature Curiosorum, vol. xix. Taf. xlvii., li., liii. 
