COMI'OSITION OF THE FLORA. 



129 



America: tho remaining 14 genera are found in 

 more than one continental area. The o 

 largest genera, Fraxinus (40 species), Mayepea 

 (50 species), and Jasniinum (160 species), tire 

 all cosmopolitan. Eight of the 21 genera have 

 l)een foiuul fcis.sil, and the family evidently has 

 an extended history, although there are no 

 known Cretaceous records worthy of credence. 

 Nor is tho record well enough laiown to war- 

 rant generalizations. It is obvious from the 

 early Eocene occun-ence of leaves of Fraxinus 

 associated with characteristic fruits thiit the 

 f amdy must have been evolved before the close 

 of the Upper Cretaceous, but none of the genera 

 have any well-marked or almndant known rep- 

 resentation until Tertiary times. 



The genus Fraxinus Linne is represented 

 by 2 species in the Wilcox flora — a character- 

 istic samara and foliage identical with that 

 described by Heer from western Greenland as 

 Fraxinus johnstrupi. Heer's species furnishes 

 an interesting example of the extended distri- 

 bution of members of the Eocene flora, at the 

 same time illustrating the northward radiation 

 of floras during the Eocene. More than 10 

 additional Eocene species are known, all of 

 which are American, ranging from Tennessee 

 to Alaska and Greenland. The Oligocene 

 marks the appearance of the genus in Europe, 

 from which time to the present the genus has 

 been represented tlu-oughout the warmer parts 

 of the North Temperate Zone, at least 4 of the 

 existing species making their appearance in 

 the Pleistocene. 



The second genus represented in the Wilcox 

 flora is Osmanthus Loureiro. It includes about 

 10 existing species of eastern North America, 

 eastern Asia, and Polynesia. The Wilcox 

 species is exceedingly close to Osmantlms ameri- 

 canus Bentham and Hooker, of the Atlantic 

 and Gulf coasts from North Carolina south- 

 ward. A second fossil species is foimd in the 

 Miocene of Florissant, Colo. 



The Old World genus Phillyrea Lume is 

 foimd fossil in Em-ope. The genus Notelffla 

 Vent enat, which contains G existing Australian 

 species and an isolated remnant of its former 

 distribution in Madch-a and the Canary Islands, 

 is represented in the Eocene, Oligocene, and 

 Miocene of Eurojje. The genus Olea Linne, 

 which includes more than 30 existing species, 

 about equally divided between Africa, Asia, ami 

 Australia and Polynesia, is represented by about 

 50243°— 16 9 



20 fossil forms (including Oleophyllum Con- 

 wentz and 01ea'car[)um Meiizel) in Europe, 

 where they range in age from the l)asal Eocene 

 through tiie Oligocene, Miocene, and Pliocene 

 to the Pleistcx'cne. The genus is not known 

 in American fossil floras, but there is a supposed 

 species in the early Tertiary of Australia. 



The genus Ligustrum Linne, which contains 

 about 35 existing species in southeastern Asia 

 and the East Indies, is repi'esented by 3 species 

 in the Oligocene and Miocene of Europe. 

 A species of Ligustrum recorded by Hollick 

 from the Upper Cretaceous of Long Island is 

 probably a Pisonia. Saporta has described 

 representatives of the genera Syringa Limie, 

 based on floral remains from tlu^ Sannoisian of 

 southeastern France. 



Tlie family Apoc_>maceiB comprises 133 genera 

 and between 1,000 and 1,100 existing species of 

 perennial herbs, vines, shrubs, and trees, most 

 of which have a milky acrid juice and simple 

 exstipulate leaves. The fruit as a riile con- 

 sists of a pair of folUcles or ch'upes and the 

 seeds of many forms are comatose. The family 

 is ahnost equaUy divided into 2 subfamflies, 

 the Plumeroidea>, which contains 68 genera 

 and about 550 species, and the Echitoideje, 

 which includes 65 genera and about 500 species. 

 The genera Plumeria Linne, which comprises 

 about 40 species, and Rauwolfia Linne, which 

 comprises about 45 species, are cosmopoU- 

 tan, mostly tropical. Twenty-four genera and 

 about 300 species occur in more than one con- 

 tmental area. America heads the list, with 36 

 peculiar genera and about 325 species, foUowed 

 by Africa, with 28 pecvfliar genera and about 

 130 species, and Asia, with 20 peculiar genera 

 and about 75 species. Australia has few 

 endemic genera or species, but numerous 

 genera range froni Asia or Africa to the 

 Australian region, and several genera are 

 peculiar to Malaysia and to Polynesia. In the 

 present state of our knowledge the distribution 

 does not fm-nish material for generalization. 



The fossil record, although it includes repre- 

 sentatives of at least a dozcMi gcrnera, is too 

 incomplete to shed much light on the history 

 of tho family or its existing distribution. The 

 largest fossQ genus is the form genus Apocyno- 

 phyllum, proposed by llecr, which embraces 

 fossil forms that resemble Thevetia, Cerbera, 

 ApocAnium, and oth(>r existing genera of the 

 famil}'. Five species which are recorded from 



