lis 



LOWER EOCEXE FLORAS OF SOUTHEASTERX NORTH AMERICA. 



through Mala_\-sia to -Vustnilia. Sassafras has 

 well-marked foliar characters of both form and 

 venation that render it readily recognizable in 

 the fossil state. More than two score fossil 

 forms have been described, the oldest of which 

 are 3 well-markeil species in the Patapsco 

 formation (Albian^ of the middle Atlantic 

 slope in Maryland and \'irginia. A species is 

 recordetl from this horizon in Portugal, but the 

 identification is very doubtful, as is also that 

 of a Cenomanian species described from 

 Bohemia, which latter probably represents the 

 genus Sterculia. In America, on the other hand, 

 the genus is widespread and well differentiated 

 at the base of the Upper Cretaceous, ranging 

 from Greenland along the coast and in the in- 

 terior to South America. It comprises about 

 a dozen known species. By Eocene time 

 Sassafras had reached Europe, where it has 

 been found throughout the Ohgocene and 

 Miocene, probably by way of the Arctic regions. 

 A very doubtful form is recorded from the 

 later Tertiary of Austraha. In the Phocene 

 the European forms had retreated southward 

 but remained common in Italy, France, and 

 Spain. The glaciation of the Pleistocene 

 caused their extinction on that continent, the 

 single existing species surviving to-day in the 

 original home of the genus. 



The order Myrtales, as developed in the 

 Wilcox flora, contains 11 species of M%Ttaceae. 9 

 species of Combretacese. 1 species of Trapacese. 

 and 1 species of Melastomatacese. as against 

 7,000 species in the existing flora. 



The family Myrtacete includes over 3.100 

 existing species, which are separated by taxo- 

 nomists into 2 subfamiUes. The first of these, 

 the Myrtoide^, comprise 32 genera and about 

 2,400 species, mostly tropical forms, more than 

 75 per cent of which are confined to the West- 

 ern Hemisphere. There are over 200 species 

 in Asia, one of which extends into southern 

 Europe, about 75 in Africa, about 200 in 

 Austraha. and about 60 in Oceaniea. Nine- 

 teen genera are confined to America, including 

 the only 3 monotypic genera in the subfamily, 

 as well as large and greatly differentiated 

 genera like Myrcia, with upward of 450 spe- 

 cies. The two other large genera. Myrtus, 

 wMch includes 178 species, and Eugenia, 

 wluch includes about 1,300 species, are the 

 only two genera found on all the continents. 

 America contains 135 species of Myrtus and 



SoO species of Eugenia, or more than 75 per 

 cent in the genus M_\Ttus and more than 65 

 per cent in the genus Eugenia. The second 

 subfamily, the Leptospermoidete. comprises 

 the Leptosperm*. which contain 2S genera 

 and about 700 species, and the Chama?laucie£e, 

 which contain 12 genera and about 165 species. 

 Both these tribes are even more strikingly 

 AustraUau than the Mvrtoidese are American. 

 The Chamielaucieje are entirely Australian and 

 mainly coutined to western Austraha. The 

 Leptosperm* include a single monotvpic genus 

 in Chile, and the distribution of the other 

 members of this tribe suggest that it shoidd be 

 placed in some other aUiance, smce with the 

 exception of Metrosideros. which is represented 

 in Africa, and the genus Bieckea. which reaches 

 the Asiatic mainland, all the genera are con- 

 fined to Australia or the sm-roimding islands 

 southeast of Asia. 



In a recent paper Aiidre\vs ' has presented 

 some interesting statistics of distribution and 

 an ingenious theory of the history of the 

 family. He considers that the original stock 

 was arborescent or shrubby and bore entire, 

 simple, opposite, pemii-veined leaves, with 

 dots and intramai^inal aerodrome veins: the 

 calvx lobes and petals were imbricate, proba- 

 bly in fives: flowers regular, sohtary or in 

 cymes: stamens indefinite, munerous, free, 

 with versatile. 2-celled anthers: ovary inferior 

 and contained two or more cells: style simple; 

 fruit inferior, crowned with persistent Hmb of 

 calyx, indehiscent. succulent, or fleshy (rarely 

 dry^ : no albmuen: cotyledons tliick and fleshy 

 with a short radicle. 



From the character of Cretaceous climates 

 this or some other theoretic prototype flour- 

 ished in a mesophytic environment. Among 

 modern groups the nearest approach to this 

 theoretical stock is fm-nished by the Myrtoi- 

 dese, which are fleshy fruited, most numerous 

 in species, and widely spread in the equatorial 

 regions, over 75 per cent of them, however, 

 being confined to America. The existing 

 Myrtacese, whose capsular fruits represent the 

 extreme of speciahzation in the family, are 

 Australian, and the Chamielaucieae, which 

 stand in an iutermechate position between the 

 two precetUng groups, are almost whoUy con- 

 fined to western Austraha. 



1 Andrews. E. C. The development o£ the natural order Uyrfaceae: 

 Linn. Soc. Xew South Wales Proc., vol. 3S, pt. 3, pp. 529-36S, 1913. 



