COMroSITIOX OF THE FLORA. 



131 



trios, trees. The family is largely tropical or 

 subtropical and is notably rcpresenti^d in tlie 

 South American region. The fossil record is 

 most incomplete. The largely Old World gc^nus 

 Clerodendron Limie is unmistakalily present 

 in both Eocene and Oligoceno of Europe, and 

 Ettingshausen has referred somewliat doubt- 

 fully determined forms from I lie European 

 Ohgocene to the An\erican genus PetnB 

 Linne and to the cosmopohtan genus Vitex 

 Linne. The genus Citharexylon Linne con- 

 tams about 20 existing species, which range 

 from the Florida Keys and Lower California 

 through the American Tropics to Bolivia and 

 Brazil. A single species found in the IloUy 

 Springs sand and Grenada formation is ex- 

 tremely close to the existing Citharexylon 

 villosum Jaccjuin, a small coastal tree of the 

 Florida Keys, the Bahamas, and tlie Antilles. 

 With the exception of one or two doubtfully 

 determined forms in the Miocene of south- 

 eastern Europe and a form described by Engel- 

 hardt from the Tertiary of Colombia it is the 

 only known fossil forni. 



The genus Aviccnnia Linne, sometimes made 

 the type of a distinct family, the Avicen- 

 niaceiJe or black mangrove family, includes 

 from 3 to 30 existing species, according to the 

 mterpretation of different students. These 

 plants are found on all tropical tidal shores. 

 Two species have been recognized in the 

 Wilcox flora, one based on leaves and the second 

 on a not conclusively identified capsule. 



The family Solanacea; mcludes about 70 

 genera and about 1,600 existing species, widely 

 distril>uted and largely tropical but extending 

 into the Temperate Zone, notably in the West- 

 ern Hemisphere. It comprises herbs, shrubs, 

 vines, or, in tropical countries, trees, which 

 bear opposite, stipulate, toothed, lobed, or 

 dissected leaves. Their fossil history is almost 

 entirely unknown. The single Wilcox rep- 

 resentative of the family is a flowi-r described 

 as Solanites, a genus founded on the some- 

 what younger remains of a similar flower 

 found in the Sannoisian of France and com- 

 parable with the existing South American 

 genus Saracha Ruiz and Pavon, as well as with 

 W^itheringia, Solanum, and similar forms. 



The last order of Gamopetalse positively rec- 

 ognized in the Wilcox flora is t\w. Rubiales, 

 wliich includes more than '),()(){) existing species, 

 segregated into 5 families. More than four- 



fifths of the species are referred ti) tiie family 

 Rul)iacefe, the only one represented in the 

 Wdcox. 



The Rubiacea3 includes about 355 genera and 

 more than 4,500 existing species of herbs, 

 slu'ubs, and trees that bear simple, opposite or 

 verticillate, mostly stipulate leaves. They are 

 widely distributed and largely tropical. Ac- 

 cording to Beccari the RubiaceiB is the largest 

 family in the flora of Borneo. It ranks second 

 in the flora of the Malay Peninsula ancl in 

 that of the Philippines, fourth in the flora of 

 Central America (llcmsley), and tlikd in that 

 of the Celebes (Koorders) . Though the Wilcox 

 representation is confined to a single species- 

 each of Exostema, Psychotria, and Guettarda, 

 great interest must attach to the fossfl record 

 of so higldy organized a family, wliich is my 

 justification for introducing the foUowing brief 

 sketch of our knowledge of it. 



No less than 27 genera have been recognized 

 m the fossil state. With the exception of the 

 very doubtful determination of a species 

 referred to, Rubia^phj'Uum from the Turonian 

 of Bohemia, wliich doutjtless is a species of 

 Ericaceae, the family is unknown in the Upper 

 Cretaceous. It is, however, represented in tlie 

 early Eocene, both in America and Europe. 

 The Wilcox forms represent a species of Ex- 

 ostema Richard, close to the existing Exo- 

 stema caribxum, Roemer and Schultes, wliich 

 ranges from the Florida Keys to Central 

 America. The genus comprises about 20 

 existing species of slii'ubs and small trees, which 

 are confined to the Tropics and subtropics of 

 America. The second W^ilcox species is re- 

 ferred to Guettarda Endlicher, a genus that 

 comprises about 50 species, most of wliich are 

 confined to the American Tropics, though one 

 or two cosmopohtan tropical maritime species 

 are included. The Wilcox form is very close to 

 the existing Guettarda elliptica Swartz, a small 

 tree of the Florida Keys, the Bahamas, and 

 the West Indies. The third Wilcox species is 

 Psychotna grand't folia, described originally by 

 Engelhardt from the early Tertiary of Ciiile. 

 The genus Psychotria Linne comprises about 350 

 (the "Index Kewensis" lists between 600 and 

 700) existing species of shrubs and small trees 

 in tropical America, Africa, Asia, and the East 

 Indies. Two-thirds of its sp(H'ies are American. 

 The fossil form is compared with Psychotna 

 (jrandis Swartz of tlie American Tropics. 



