COiMI'OPITIO.X (>K TITK l''l,()l!.\. 



125 



appear to bo more conipMcl and iintui-al t;;r()ii])s 

 than tlio ('orrcsjxmdiii^ alliances among the 

 Choripetala:>. The Krieales. I'limuhiles, and 

 Ebeiiales are |)enlacveli<- and isocai'pons, hnl 

 th('(jentianales,Polenioniales. l'ersoii;des,Phin- 

 tagiiiales, IJnhiales, Valeriaiiah's, and Cani- 

 panuhilos are tetracyclic and anisocarpic, the 

 last throe orders Ijoinij episivnons. 



'rh<' lierl)aceous i'ornis ol' tiie alJiance pre- 

 dominate and several of the families are dis- 

 tinctly horesil. Though theComjiosita", Lai)iata', 

 and Plantaginacese are of \\cirld-\\i(h' distril)ii- 

 tion, there are no notable continental |)airings, 

 such as usually accompany an extended geologic 

 history. These and many otiier facts suggest 

 that the Gamopetaho as a whole, especially the 

 more evolved, herbaceous. extratro])ical fami- 

 lies, are of relatively modei-n origin and that 

 their major specific differentiation was concomi- 

 tant with their occupation of tlie Temperate 

 zones after the retreat of tiio Pleistocene ice 

 sheets. 



The so-called Composita? are, from tlie view- 

 point of floral structures, clearly the culmination 

 of tlie evolution of floral structures, as is shown 

 not only by their gamopotaly, epigyny, coimi- 

 vent anthers, and tiie formation of seedlike 

 fruits with a pappus but by the complex flowei'- 

 head, the prevalence of diclinism, the dimor- 

 phism of the corollas, and ot lier special features. 

 This evidence is corro])orated by the general 

 modernness of the alliance. 



Six gamopetalous orders are represented in 

 the Wilcox flora. The first of these, the Pri- 

 mulales, in its fullest development in cxistmg 

 floras mcludes the three families MjTsinaceaa, 

 Primulacea', and PlnmbaginacefP. They are 

 structurally much alike and have a single cycle 

 of stamens opposite the petals and a unilocular 

 ovary with a free central placenta. Thi^ com- 

 munity of floral organization can only bo at- 

 tributed to convergence and notr to filiation, 

 since the Myrsinacea^ are old forms whicli in 

 modern floras are predominantly ti-opical and 

 American, whereas the Primulacea^ are ciiielly 

 North Temperate and bor(\al lierbs of relatively 

 recent evolution, and tiie Plumhaginaceaj are 

 very modern halophytic herbs and undershrubs 

 of salt beaches and stopp(>s, mostly of the Med- 

 iteiTaneau and Casj)ian i-cgions. 



The Myi-sinaceae, the only family represented 

 in the Wilcox flora, is characterized by alter- 

 nate, simple, coriaceous, puncttate, exstipulate 



l(>avos; ])erfect. regular (lowers; and single- 

 seeded drupac(M)us fruits. 



The family contains al)out ;•!() genera and n.'A) 

 existing s|)ecics of shrubs or trees, la.rg(4v trop- 

 ical and predominantly American. Thus. 1 1 

 gencrji and more than 2()() species ai-e peculiar 

 to America, only 4 g(Miera and loss than a dozen 

 species are p(H-uliar to Asia, and :i goiu^ra and 

 about 100 species are ])eculiar to Africa. 



The genus Myrsine Liune is found in all the 

 continents except lilurope and hi Polynesia. 

 Its distriliution is extratropical in the African 

 region. Euardisia Pax is found in all the Trop- 

 ics. Maesa Fiirskal lives in all oriental tropical 

 Countries as does also the monotypic genus 

 /Egiceras Gartner, a member of the coastal man- 

 grove association. The genus Cybianthus Mar- 

 tins, largely South American, is represented by 

 species in the Philippiiu^s and in New Grenada. 

 There is little that is signilicant in the recent 

 distribution of the family, and the fossil record 

 is very incomplete. 



More than 75 fossil forms have been referred 

 to Myrshie, the oldest of which are the 7 or 8 

 forms recorded from the Upper Cretaceous. 

 AU the older of these forms (Cenomanian) come 

 from North America, and only one, from the 

 Turonian of Bohemia, occurs in the European 

 Upper Cretaceous. The ^Vmerican forms are 

 not varied specifically, but have a wide range 

 and are common, extending from the Atane 

 beds of Greenland along the Atlantic coast to 

 the Tuscaloosa formation of western Alabama. 

 They ai-e also found in the Dakota sandstone of 

 the western interior region. 



The Eocene records of Myrsine number 7 or S 

 species and include an early Eocene form of 

 Alum Bay, 3 in the upper Eocene of France, 

 and 2 m western Alaska. M.>Tsine is exceed- 

 ingly varied and abundant dui-ing the Oligo- 

 cene throughout southern P^uropc, more than 

 80 species having been described, of which 1 1 

 occur in the basal Oligocene of southeastern 

 Franco (Sannoisian). There are more than 30 

 Miocene species throughout Europe, one from 

 Colorado IxMng the only known Anuirican 

 occurrence. One species is also roconhnl from 

 Australia. Several species linger in the Plio- 

 cene of southern Europe in France and Italy, 

 and one species is found in the Pliocene of 

 Brazil. In addition to the forms referred to 

 Myi-suio several forms from the Eurojioan 

 Ti-rtiary have been referred to the form genus 



