COMPOSITION OF THE FLORA. 



121 



only by chiiractcristic loiives but by fl(>w(M's 

 and fruits. No spccios arc certainly known 

 fi'iini luirizons as old as tli(> U|)|)cr ('rctaccous, 

 allhoui^h a s])('<-i('s of Tcrniinaliphylluiu luis 

 been described {nnn tlie Perucer beds (Ceno- 

 inanian) of Bobeniia, a sp(>cies of ('onil)reli- 

 pliyllum from tiie Upper Cretaceous of tlie 

 Kanaerun (West Africa), and a species of Cono- 

 carpites from the Tuscaloosa formation of Ala- 

 bama. So far as I know there are no autiicMi- 

 tic occurrences as old as those of the Wilcox. 

 In tliis flora there are 3 well-marked speci(>s of 

 Combretum, a genus that contains about VSO 

 existing species found in all tropics except 

 Australia and Polynesia. More than .30 of 

 these species are endemic in South America, and 

 their alnnidance in the Wilcox, as well as t]ii> 

 occurrence of a sj^ecies in the early Tertiaiy of 

 Cliilc, strongly suggests that the genus is of 

 American origin. This statement, as well as 

 tiie (h'termination of the Wilcox species of 

 leaves, receives confirmation in the remarkably 

 preserved flower from these beds described as 

 Combref ant bites. Combretum has been re- 

 corded from the Miocene of Switzerland and 

 Germany and from the Pliocene of Italy. It 

 occurs in the Claiborne group of tiie Mississippi 

 (Mubayment, and Felix has described petrified 

 wood fron^ the supposed Eocene of tlie Caucasus 

 which he calls Combretacinium. 



The genus Conocarpus Gartner, a member of 

 the tro]Mcal mangrove association, is repi'c- 

 sented by a well-marked species in the Wilcox 

 flora that is supposed to be descended from tlie 

 Conocar])ites described from the Tuscaloosa 

 format ion in this same general region. Another 

 species very close to the modern form of the 

 American Tropics occurs in tiie Claiborne group. 

 Fruits of Conocarpus have also been described 

 recently from the Aquitanian of Rhenish 

 Prussia. 



The genus Laguncularia Gartner, mono- 

 typic in tiie mangrove association of America 

 and the west coast of tro])ical Africa, is repre- 

 sented by both leaves and fruits in the Wilcox 

 flora. Tlie only otiier genus of (\)mbretacese 

 that has Icnown fossil representatives is Termi- 

 nalia Linne. It is a large genus in the existing 

 flora and contains more than 100 species almost 

 equall}' divided between America, Asia, Africa, 

 and Australia; several of tiie species arc very 

 wide-ranging littoral ty])es. There are 3 Wil- 

 cox species, based on botli leaves and fruit. 



One of llio species makes its appearance in the 

 uiuh-rlying Midway ( '.) formation of f lie western 

 Gulf region and possildy represents tlu^ l)e- 

 ginning of its extension northward along tlie 

 coast in the enit)ayment region from tropical 

 America. It continues in this i-egion as lafo 

 as the upper Kocene after nearly tiie entire 

 Wilcox flora iiad been replaced by difi'crent 

 foi"ms. 



Five Oligoccuie s]>ecies of Terininalia liave 

 l)een described from Europe, the determina- 

 tions resting on both leaves and fruits. The 

 occurrences range from the Samioisian to tlie 

 Cliattian and geograpliically from southeastern 

 France to Greece. There are 7 well-distributed 

 Miocene species in Europe, as well as Pliocene 

 species in botli Spain and Italy along the shores 

 of llie Pliocene Mediterranean Sea. A su])- 

 posed Pliocene species is also recorded from 

 Bolivia. 



Though future discoveries must greatly am- 

 plify the fossil record before the Jiistory of the 

 family in past times can be traced with any 

 degree of surety, the remarkable display of 

 those forms in the Mississippi embayment 

 region, evidently derived from the American 

 Tro|>ics, gives mucli probability to the theory 

 tliat the family originated in tlie American 

 Tropics during the Upper ('retaceous. 



The genus Trapa Linne formerly included in 

 the family Onograceas, is now made the type 

 and onl}^ genus of tiie family H3-drocar\'acetB 

 (Trapacese Dumortier, 1827). There are 3 ex- 

 isting species, aU aquatics and all confined to 

 the Old World except for the natm-alizatioii of 

 Trapa natanti Linne in New England and New 

 Yorl<;. This species is irregularly scattered 

 throughout central and southern Europe, 

 though its area of distribution is contracting, 

 as is showm by its occurrence in postglacial de- 

 posits at many localities b(\yond its present 

 range in Russia, Finland, vSweden, and Den- 

 mark. The two other existing species are 

 Trapa bicornis Linne of Ciiina and Trapa, hi- 

 spinosa Roxburg of southeastern and s()utlu>rn 

 Asia, which is said also to occur in Africa. 



The genus has an extended geologic history. 

 Rosettes supposed to represent the floating 

 leaves {Trapa? mirroplyUa Lesqu(>rcux and 

 Trapa? cvncata Knowlton) are widespread in 

 tlu! Rocky Mountain province in beds of late 

 Cretaceous and early Tertiary age. The oldest 

 recognizable fruits are a large bicornute form 



