VEGETATION OF THE STRAND. 587 



classification adapted in one case may not be so serviceable in 

 another. For example, the action of surf on the strand forma- 

 tions will be different on the shore of a lake not frozen over during 

 the winter, when the high winds carry the wave action higher up 

 than in the summer. Ocean tides also tend to complicate the 

 strand formations beyond what is seen on the shores of Jakes or 

 ponds. Along salt bodies of water also a halophytic type is 

 developed on rocky shores and in salt marshes, and to a limited 

 extent on the mid-strand sandy shores. 



The flora of the strand bears a very close relation to its physi- 

 ography, and can only be understood when studied in connection 

 with the physical geography of the region,* and in an endeavor 

 to trace the evolution of the plant formations, i.e., the part which 

 plants have played in determining the physical geography of 

 the strand, as well as the influence of environmental factors on 

 the plant formations. 



1078. Variations in the shore. Variations in the topography 

 of the shore offer very different conditions for plant life, so that 

 a great variety of edaphic formations are developed. These 

 variations take place in three general directions: ist, the gradi- 

 ent of the shore, whether precipitous as shown in the bluff, or 

 very high steep banks, or in the lower grades down to a gradual 

 slope toward the interior country; 2<i, the mechanical condi- 

 tion of the shore material, whether of solid, smooth-surface 

 rock or cieviced rock, boulders large or small, talus, gravel, 



* MacMillan (1897) was the first one in America to apply this principle 

 to the study of plant formations. (See observations on the distribution 

 of plants along the shore at Lake of the Woods. Minn. Bot. Stud., Vol. I., 

 Bull. 9, 949-1023, May, 1897.) In concluding he says: "No extended 

 summing up is necessary, for it must be apparent that the purpose of the 

 paper has been but a single one to point out the dependence, over such 

 an area as the shores of the lake, of plant formations upon topographic 

 and environmental conditions. It has been shown how each formation 

 may be explained briefly as connected with a certain melange of outward 

 conditions both by themselves and as connected with the growth of the 

 vegetation." 



