96 CARNEGIE INSTITUTION OF WASHINGTON. 



length and breadth of 30 species, not including Acacia, has a length of 

 64 mm. and a width of 5 mm. A similar leaf built on the measurements 

 of 16 species of Acacia is 84 mm. long and 3.5 mm. wide. Results 

 derived from constructing ratios based on the relation between area, 

 one side, and length further illustrate the point. In the case of circular 

 leaves this ratio is approximately 1 : 54.3, and in linear leaves it is 

 nearly 1:1. In the largest leaf -size class for ''microphylls" of Raun- 

 kiaer the ratio is approximately 1 : 23.6. The ratio of leaf-area to 

 leaf-length for 29 species of desert and arid perennials from South 

 Australia is 1 : 4.7. So far as these dry regions are concerned, there 

 are relatively few species having the least ratio, and these do not 

 necessarily live in the driest habitats, although the ratio for such 

 species is necessarily low. 



Ecology of the Strand Vegetation of the Pacific Coast of North America, 

 hy William S. Cooper. 



The sand-dunes and beaches are the principal field of study, but 

 cliffs, blufTs, and salt marshes are incidentally involved. The special 

 value of the study with regard to development of the fundamental 

 laws of the science of ecology lies in the fact that the initial soils of 

 beach and sand-dune are everyw^here extremely similar, if not almost 

 identical, and that any striking vegetational differences must be cor- 

 related wdth climatic factors. There is here, therefore, an excellent 

 opportunity to investigate the effects of climatic control upon distribu- 

 tion, ecological character (form, structure, function), and successional 

 development. 



The general method used is a combination of extended exploration 

 and thorough study of carefully selected localities. The latter phase 

 must include (1) measurement of habitat factors; (2) investigation of 

 plant form and structure (root system, conductive system, leaf); (3) 

 determination of the courses of the successions leading to the climax 

 in each region, involving the establishment of permanent quadrats and 

 transects; (4) experimental greenhouse work to check the observa- 

 tional results wherever possible. 



The month of May was spent in a careful study of the strand vegeta- 

 tion from the Coronado Hotel to the Tia Juana River, a stretch of 16 

 kilometers. Vegetational development proceeds along two lines. In 

 the first, beginning in fresh-blown sand, Ahronia maritima is the 

 principal pioneer. This plant, because of a persistent negatively 

 geotropic tendency in the branches, coupled with scanty development 

 of mechanical tissue, builds dunes which increase rapidly in height so 

 long as the accumulating sand supports the shoots in their erect posi- 

 tion. WTien, because of increase in height of the dune or from any 

 other cause, the upward building slackens, the weight of the shoots 



