122 



LOWER EOCENE FLORAS OF SOUTIIEASTERX NORTH AMERICA. 



from the Eocene of Canada and Alaska and Trapa 

 ii-Ucoxensifi of the Wilcox flora. Two supposed 

 upper Eocene species o(;ciir in the Payette for- 

 mation of Idaho. An Oligocone species {Trajxi 

 credneri Schenk) has been lU^scribed ivom Sax- 

 ony, and no less than 5 species have been 

 described from the Miocene, 1 occurring in 

 Japan and the rest in Europe, where 2 species 

 continue into the Pliocene. A species from 

 the late Phocene of America is found in south- 

 ern Alabama. The existing Trapa natans has 

 been recorded from the preglacial beds of 

 England and Saxony and from very many 

 hiterglacial and postglacial deposits in Portugal, 

 Italy, Netherlands, Germany, Sweden, Russia, 

 and Denmark. Guimar Andersson in a paper 

 published in 1910 mentions 18 localities in west 

 Prussia, 6 in Denmark, 17 in Sweden, and 29 

 in Finland. 



Tlie family Melastomatacei» is relatively large, 

 prevaiUngly shrubby rather thim arborescent, 

 and includes about 150 genera and more than 

 3,000 existmg species. It comprises distinctly 

 humid types and is almost strictly tropical, 

 although some members range southward to 

 40° south latitude. Although it abounds in 

 Malaysia, it is a typically American family, 7 

 of the 15 tribes into which the family is divided 

 being confined to tropical America, and about 

 2,500 of the existmg species being also endemic 

 in this region. It ranks ninth m Hemsley's 

 flora of Central America and abounds in the 

 West Indies and especially in Brazil. Though 

 the geologic history of this vast assemblage of 

 forms is practically unknowm, there is no evi- 

 dence to disprove the theory that, like the 

 allied families Combretacese and Myi-taceae, 

 the Melastomataceae had .its origin in that most 

 prolific; region — the American Tropics. 



The few fossil forms that have been found, 

 inchuHng leaves, flowers, and calices, have 

 been referred to the form genus Melastomites, 

 first proposed by Unger. A doubtfully de- 

 termined species, which probably belongs to 

 the Lauracea?, has been recorded from the Upper 

 Cretaceous of Westphalia. Th(> only known 

 Eocene species is the well-marked form present 

 in the Wilcox flora. Four Oligocene species have 

 been described from Bohemia, Styi'ia, and Egypt ; 

 4 Miocene species from Switzerland, Prussia, and 

 Croatia; and a Pliocene species from Italy. 



TheorderUmlxdlales (I'nibelliflonrof Ejigler) 

 includes onlv three families, the Araliaceae, 



Umbellifene, and Cornacea-, but more than 

 3,000 existing species, of which nior(> tlian two- 

 thirds belong to the Umbcllifcru'. Tlie thr(>e 

 families are closely related and stand somewhat 

 apart from the rest of the choripetalous orders. 

 Thougli undou])tedly there has been great 

 specific variation m modern times, especially 

 among the licrbaceous forms of Umbellifer£e, 

 some members uf the alliance go back as far as 

 undoubted dicotyledons have been found, and 

 this fact is one of the strongest arguments for 

 considering its relationships to the GamopetaljE 

 to be less close than some botanists have sus:- 

 gested, a suggestion based primarily on a con- 

 sideration of the floral structures apart from 

 the morphologic features of the whole ])lants. 

 As regards floral evolution the Umbellales 

 clearly mark the highest expression among the 

 ChoripetaliB and parallel the Gamopetala;. 

 The flowers are epigynous, the stamens cyclic, 

 the carpels reduced, and the sepals commonly 

 reduced. The Araliacete and Cornacese are 

 both rejiresented in the Wilcox flora and the 

 UmbelliferiB doubtfully so. 



The family Araliacese contains about 52 

 genera and 500 existing species, chiefly m- 

 habitants of the Tropics, though notable 

 exceptions are found in North America and 

 eastern Asia. The modern center of develop- 

 ment is in Asia and Australia, no less than 3.3 

 genera being confined to Asia, Malaysia, ,\us- 

 tralia, or Polynesia. Africa contams 3 peculiar 

 genera and about 30 species and America 5 

 peculiar genera and about 100 species. The 

 genus SchefBera is cosmopolitan. Hedera and 

 Polycias occur in P^urasia and Africa. Two 

 genera arc common to Asia and America, and a 

 third (Aralia) is found hot only in these conti- 

 nents but in Australia. Pseudotenax wliich 

 contains about 6 species is peculiar to western 

 South America and New Zealand. 



The fossil record is not nearlj^ complete 

 enough to afford a secure basis for generaliza- 

 tions. Several genera are found, howev(>r, in 

 the oldest deposits in which undoubted dico- 

 tyledons are known. The largest genus is 

 Aralia, which is commonly used by ])aleobotan- 

 ists as a form geims for generically mudentified 

 species of Araliaceic, rather than for forms 

 fallhig withm a strict modern definition of 

 Aralia. No less than 50 species of Aralia have 

 been described from the Cretaceous, 2 of which 

 come from horizons as old as the Albian of 



