DEPARTMENT OF BOTANICAL RESEARCH. 89 



6. The marine marshes of the Atlantic coast in the neighborhood of New York and along 



the east coast of Florida. 



7. Mangrove swamps on the coast of Jamaica, and from Cape Florida to about the north- 



ern limit of the species in the Indian River region. 



8. Strand vegetation on the Atlantic Coast, in the latitude of New York and along the 



Florida coast. 



9. Preliminary studies on the Florida keys. 

 10. The Everglades, Florida. 



During the year an account of the montane rain forest of Jamaica 

 has been pubhshed (Amer. Jour. Bot., vol. iv, pp. 268-298), the man- 

 grove swamps have been treated in a preUminary way (Biol. Bull., 

 vol. XXXII, pp. 202-211), and a general account of the work given 

 (Science, n. s., vol. xlvi, pp. 25-30). 



Two months have been spent in southern Florida and on the Indian 

 River, with the assistance of Mr. Charles W. C'rane, in field work. 



Rate of Growth in relation to AUitudi7ial Conditions, by Forrest Shreve. 



Work was begun several years ago with a view to ascertaining the 

 extent to which the rate of growth and density of stand of the yellow 

 pine are influenced by the dissimilar conditions of different altitudes. 

 This work has been prosecuted mainly on the Santa Catalina Moun- 

 tains, in the vicinity of the stations at which climatological records 

 have been secured. Some of the more general results of the work have 

 been elaborated and prepared for publication. 



The number of pine trees more than 10 cm. in diameter increases 

 with altitude from 6,000 to 9,000 feet, as enumerated for areas of the 

 same size. These elevations are near the lower and upper hmits for 

 the distribution of this tree. The total stump area and total volume 

 of the adult trees increases still more sharply with altitude. The 

 actual number of trees at 6,000 feet is slightly greater than at 7,000 

 feet, but the number at the former elevation is largely made up of 

 very young individuals. The rate of growth was determined by ring 

 count and diameter measurement of selected trees of all sizes and all 

 types of crown. A comparison of the curves for rate of growth at 

 6,000, 7,000, 8,000, and 9,000 feet on south-facing slopes and for 6,000 

 and 7,000 feet on north-facing slopes shows a remarkable similarity 

 in all cases except the 9,000-foot area, where the rate was much higher 

 than at lower elevations. Through the vertical range of the yellow 

 pine in the Santa Catalina Mountains there is a sharp gradient of 

 change in all of the leading climatic conditions. That these changes 

 should be without influence on the growth of the dominant tree of 

 these elevations can be explained only on the possibility that there is 

 a compensating operation of the conditions. The increase of rainfall 

 from 6,000 to 8,000 feet (and in most years to 9,000 feet) favors 

 increased growth, but the decrease in the length of the frostless season 

 on ascending through these altitudes is calculated to lessen the total 



