. The later extinct floras of North America [microform]. Paleobotany; Paléobotanique. ,M:imWV. 104 THE LATER EXTINCT FLORAS OF NORTH AMERICA. spring seven or eight pairs of lateral nerves above the basilar pair; these diverge at an angle of about 35 degrees, are slightly flexed at the base, straight or nearly so above, where they are somewhat truncated, their branches terminating in the marginal teeth. The basilar nerves diverge from the midrib at an angle of about 35 degrees and run nearly straight to the extremities of the lateral lobes. They each give off on the lower side seven or eight br
. The later extinct floras of North America [microform]. Paleobotany; Paléobotanique. ,M:imWV. 104 THE LATER EXTINCT FLORAS OF NORTH AMERICA. spring seven or eight pairs of lateral nerves above the basilar pair; these diverge at an angle of about 35 degrees, are slightly flexed at the base, straight or nearly so above, where they are somewhat truncated, their branches terminating in the marginal teeth. The basilar nerves diverge from the midrib at an angle of about 35 degrees and run nearly straight to the extremities of the lateral lobes. They each give off on the lower side seven or eight branches, of which the second or third is strongest. These are more or less curved and branched, the branches terminating in the teeth of the margin. Fruit two to three lines long, prismatic, ; Collected by Dr. F. V. Hayden. V: . This fine species, which is well represented in the collection, is closely related to Platanus aceroides, so common in the Miocene strata of Europe. There are, however, noticeable differenceii, which seem to me to have a specific value. The leaves of F aceroides, though exhibiting a great variety of form, are, I believe, always acutely toothed, while in the specimens before us the teeth are never acute, except those which in the young leaves represent the lateral lobes of the mature form. In P. aceroides also, accord- ing to Heer (Fl. Teit. Helv., Vol. II, p. 71, PI. LXXXVII and LXXXVIII, figs. 5-15), the nervation is more sparse, the angle of divergence of all the nerves greater, the number of lateral branches of the midiib less, and the number of marginal teeth considerably greater. Professor Heer says (loc. cit.) that in P. aceroides the middle lol-o of thr, leaf has two to three denta- tions on either side, while in P. Haijdenii the mature leaf has eight to ten teeth on each side of the middle lobe. The diff"erence before specified in the form of the marginal teeth is very marked and strikes the eye at a glance. In P. aceroides the
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