TRANSACTIONS OF WAGNER 

 66 



VEGETATION OF SOUTH FLORIDA 



the strand. The middle beach is marked by a great variety of univalve and 

 bivalve shells and has a wet depression behind the shells washed ashore. It 

 supports radiate masses of Sesuvium portulacastrum L., with pink flowers, 

 together with the trailing spikegrass, Distichlis spicata (L.) Greene (Plate I, 

 Fig. i). The upper beach slopes gradually up to the outer dunes, and the veg- 

 etation of both blend together, so that it is difficult to make a sharp distinc- 

 tion between the plants typic of the upper beach and those found on the outer 

 dunes. The characteristic plants of the upper beach are Ipomoea pes-caprae 

 L. (Sweet), Canavalia lineata (Thunb.) DC., Pharbitis (Ipomoea) cathartica 

 (Poir) Choisy, and the bur-grass, Cenchrus Carolinianus L. The Spanish-bay- 

 onet, Yucca aloifolia L., is found on the upper beach with occasional seaside- 

 grape, Coccolobis uvifera (L.) Jacq., and buttonwood, Conocarpus erecta L. 

 Several low shrubs are noteworthy as elements of the upper Gulf beach vegeta- 

 tion, viz., Lantana ovatifolia Britton, Ernodea littoralis Sw., and Scaevola 

 Plumieri Vahl. 



The bay beach of Sanibel Island follows the irregular curves of the 

 shore. It is comparatively narrow and the lower beach is flat. The upper 

 beach and the middle beach may be considered to merge, as the surf is of 

 little consequence as a factor in shaping the beach form. Here the conditions 

 are more favorable for the growth of beach plants than are those found on the 

 Gulf beach. The absence of a strong surf, the reduction of the force of the 

 wind, and the reduction in the salinity of the water caused by the entrance of 

 the fresh water of the Caloosahatchee River, are all environmental differences 

 which account for the greater variety of plants on the bay beach. On the 

 bay beach are washed ashore masses of the water-hyacinth, Piaropus (Eich- 

 ornia) crassipes (Mart.) Britton. introduced into Florida about 1890 at Edge- 

 water about four miles above Palatka* and which has migrated across the 

 state in a surprisingly short time. It reached the Caloosahatchee River by 

 floating in rafts down the Kissimmee River from central Florida across Lake 

 Okeechobee, through Three Mile Canal into the Caloosahatchee River, where 

 it is found in large rafts that have finally floated out to sea, or been washed 

 ashore, as at Sanibel Island upon the coastal islands. The captain of the 

 steamer Gladys, which makes regular trips to the coastal islands, informed me 



* Webber, Herbert J.: "The Water Hyacinth and its Relation to Navigation in Florida." 

 Division of Botany, U. S. Dept. Agric., Bulletin 18, 1897. 



