DESCRIPTION OF SPECIES— DLMACE^. 187 



is a tiee of moderate size, with tivc-palmalo, serrulate, dark green leaves, 

 emitting, when bruised, a pleasant fragrance by the exuding of a sweet-scented 

 glim. The species has a wide range of distribution, being most frequent in 

 the southern district of our llora, as marked in Gray's Statistics, even passing 

 above its northern limits and descending to South Florida and Mexico. It 

 has, like Platanus, a close relation to an Oriental congener, Liquidamhar ori- 

 entale, Mill., indigenous of Asia Minor; two other species, with pennincrvate 

 leaves, not l()l)ate, inliabit the East Indian region, Java, and C'liina. Another, 

 with tripalmately divided leaves, has been more recently discovered in Japan. 

 To the present time, no leaves of Liquidmnhar have been recognized in 

 the specimens from the Lignitic of the Rocky Mountains. The genus is, 

 however, represented in the Miocene Flora of Alaska by Heer, p. 25, pi. ii, 

 fio-. 7 and in a more recent formation, that of the Chalk Bluifs of California, 

 it has numerous leaves of a species closely allied to the living L. styrncijluum. 

 I have described as referable to Liquh/amhar some leaves from the Creta- 

 ceous deposits of the Dakota group. As they have the borders entire, they 

 typically ditTcr from tlie genus, as far at least as it is represented at our time, 

 and, therefore, this reference is doubtful. Though it may ])c of the origin 

 o( Liqui/famhar, its presence is positively traced on this continent as tlir back 

 as the Miocene. -Europe has until now two fossil species with serrate leaves 

 from the same formation, and a tiiird, L. Gaepperti, Walt., from the Paleocene, 

 whose leaves have the borders entire, bearing to the norinal form the same 

 relation as L. integrifoUum, Lesqx., of the Dakota group. 



URTlCINEiE. 



U L M A C E M. 

 ULMUS, Linn. 



The Elm leaves are short petioled, ovate-acuminate or broadly lanceolate, 

 pointed, doubly acutely dentate or s(!rrate, with a more or less inequikitcral 

 base, and a pinnate nervation, of clo.se, deeply marked, secondary veins, 

 ascending at first straight toward the borders, and then curving up, in enter- 

 ing the teeth, as craspedodrome. The species of this genus are at our present 

 time about equally distributed in the northern hemisphere, nine of its eighteen 

 species being Asiatic (four of them in China), four European, and six Ameri- 

 can. Except U. Mexicana, which Liebman found in the western declivities of 

 the Cordilleras, all the American species inhabit the northeastern slope of 



