296 IN LOWER FLORIDA WILDS 



of the two oceans restdted after which reelevation 

 of the area closed the strait. After separation 

 conditions differed a little on each side; the water 

 of the western ocean was cooler than that of the 

 eastern and food conditions may have slightly 

 differed. Species most susceptible to environ- 

 ment began to change, and so we have the cases 

 of two forms so similar but not quite identical in 

 the two seas. The animals least susceptible to 

 environmental change modified but little or not 

 at all, and hence the cases of specific identity on 

 the two sides of the isthmus. 



The flora of the seashore is extremely inter- 

 esting. Along sandy beaches and dunes, espe- 

 cially on the west coast, a tall, handsome grass 

 (Uniola paniculata) grows in great abundance. It 

 has ample, nodding panicles of oval flower heads 

 which look as if they were braided and keep 

 long as everlastings. Sccsvola plumieri is an at- 

 tractive low plant with thick, glossy leaves and 

 pretty white flowers that are cleft to the base on 

 one side. In sheltered spots a sunflower (Heli- 

 anthus debilis) carpets the sand and displays its 

 brilliant yellow flowers during most of the year. 

 In moist places a succulent plant somewhat 



