DESCRIPTIONS OF SPECIES. 107 



each of the basilar nerves diverge about the same number of pairs of 

 branches as from the midrib, and these are also nearly straight and parallel, 

 and terminate directly in the margin. Of these the second or third 

 exterior one on each side is often much the stronger of the series, and is 

 then prolonged into a small but distinct lateral, triangular, acute lobe, 

 giving the leaf a somewhat pentagonal form. From this basilar branch of 

 the lateral nerves, twelve or more short, generally simple, branchlets spring 

 on the lower side, and four to five on the upper side near the summit, all 

 of which terminate in the margins. The tertiary nerves connect the 

 adjacent secondary nerves nearly at right angles; sometimes they are 

 straight and parallel, but oftener more or less broken and branching where 

 they meet, near the middle of the interspaces. Where the systems of 

 nervation of the lateral and middle lobes come in contact, the tertiary 

 nerves are stronger and form a somewhat irregular network, of which the 

 areolae are large and subquadrate." 



Collected by Dr. F. V. Hayden. 



In general aspect these magnificent leaves are considerably unlike 

 those of any known species of Platanus, and I have felt some hesitation in 

 referring them to that genus. The texture was evidently thicker and the 

 surfaces smoother than in the leaves of most Sycamores, and, on the whole, 

 they recall the leaves of Cecropia or some other of the broad, leathery, 

 polished leaves borne by the trees of the tropics. On close examinatiou, 

 however, they are found to present the radical structure of the leaves of 

 Platanus, and, aside from their association with so many genera plainly 

 belonging to the flora of the temperate zone, their form and nervation 

 seem to me to afford at least presumptive evidence that they were borne 

 by a tree of that genus. They will, perhaps, suggest to the fossil botanist 

 the leaves described- by Unger under the names of Platanus Hercules, 

 P. Jatrophcefolia, etc. (Chlor. Prot, p. 137, PI. XLV, figs. 6, 7, etc), and 

 which he subsequently removed from that genus. But those palmate, 

 many-lobed leaves were very unlike these now before us, and resemble 

 much more the leaves of Jatropha or Sterculia than those of Platanus. 



The crowded, somewhat heavy and regular nervation of these leaves, 

 their thick texture and polished surface, must have given the tree on which 

 they grew an aspect quite different from that of P. occidentalis; but 

 P. orientalis, and sometimes P. racemosa, have thick and polished leaves, 



