OP MARINE COASTS. 75 



Pacific Coast of Central America. 



The writer's experience of this coast is limited to the sandy beaches 

 at Champerico in Guatemala. The slope of the beach is nearly 50°. 

 This unusual steepness is accounted for by the heavy breakers which 

 here strike the coast with full force, and the strong undertow which 

 erodes the submerged beach. The sand was coarse and very little drift- 

 ing occurred. 



Sand Formations at Vera Cruz, Mexico. 



These are very extensive and all phases of development can be ob- 

 served. Sand was drifting at the time of my visit and the formation 

 of ripples was perhaps more clear in all its details than at any other 

 place I have seen. The dunes moved rapidly, unchecked by any vege- 

 tation. The sand contained a considerable amount of lime which added 

 to the light color. 



III. PRINCIPAL COMPONENTS OF THE SAND 

 STRAND FLORA. 



In presenting a list of the principal representatives of the flora on 

 sandy sea shores, I do not intend to discuss the systematic relation or 

 the specific characters of these plants. For ecological purposes this is 

 of minor importance, at least in the present state of ecological knowl- 

 edge, and in the study of this flora I have often found it to be of greater 

 significance to consider many of the collective species, which have been 

 divided by recent systematists, as "geographical species," whose distribu- 

 tion represents a distinct whole, rather than as systematic units. 



As a taxonomic account I give a list of the principal plants occurring 

 on coastal sand formations, with a short description of the vegetative 

 parts of these "species," showing adaptations to the physical conditions 

 of environment. This list does not pretend to be exhaustive, and con- 

 tains principally those plants only which have come under the writer's 

 personal observation. 



