62 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



COEYLUS OKBICULATA Newb. 

 PI. XXXII, fig. 4. 



Ann. N. Y. Lye. Nat. Hist., Vol. IX (April, 1868), p. 58; Ills. Cret. and Tert. PI. 

 (1878), PL XV, fig. 4. 



"Leaves small, orbicular, or nearly so, slightly and unequally cordate 

 at base, blunt-pointed above; margins set with fine and nearly equal teeth; 

 nervation strong; midrib curved and slightly sinuous; lateral nerves about 

 seven pairs, mostly straight and nearly parallel among themselves, lower 

 pair sending off each seven to eight short, simple or forked branches which 

 terminate in the teeth of the edge; second pair supporting each about three 

 branches of similar character; upper lateral nerves simple, or having each 

 two to three branches near the summit; tertiary nerves parallel, distinct." 



Collected by Dr. F. V. Hayden. 



This is another hazel-like leaf, of which, without the fruit, the classifi- 

 cation must be somewhat doubtful. The general form is more like that of 

 the leaves of Tilia (T. Americana and T. Europcea), being much rounder than 

 those of any species of Corylus with which I am familiar. The nervation 

 is, however, different from that of Tilia and is, in fact, altogether that of 

 Corylus. In Tilia the leaves are usually broadly cordate; the nervation 

 of the base and lateral portions of the leaf being supplied from the first or 

 basal pair of lateral nerves, which are largely developed, much branched, 

 and reach considerably above the middle point of the lateral margin. In 

 Corylus, on the contrary, the basal nerves are short and supply only the 

 basal margins; the second pair of lateral nerves is relatively more devel- 

 oped than in Tilia, Morus, etc., and in the number and parallelism of the 

 lateral nerves their leaves approach more nearly to the strictly feather- 

 veined leaves of Fagus, Alnus, etc. 



Since the above description was written Professor Heer has published 

 his splendid series of volumes on the arctic flora, and has in a number of 

 places made reference to or given figures and descriptions of Corylus Mac- 

 Quarrii, which shows that this was a very variable species, and perhaps the 

 leaf under consideration, to which from its circular form I gave the name 

 C. orbiculata, is but one of the numerous vai'ieties of this plant, which seems 

 to have been widely spread over all the North American continent during 

 Tertiary times. Further collections made in the country bordering the 



