640 JOURNAL OF FORESTRY 



A Preliminary Study of Clitnatic Conditions in Maryland, as Re- 

 lated to Plant Growth. By Forman T. McLean. Physiological Re- 

 searches, Vol. 2, No. 4. February, 1917. Pp. 129-208. 



In this study, the author has been able, with comparatively simple 

 methods, and in the short period of time represented by one growing 

 season, to bring out some new relationships between climatic factors 

 and plant growth. The contrasts obtained between a coast and moun- 

 tain climate will be particularly interesting to ecologists and foresters 

 engaged in the study of the characteristics of mountain climates. 



The purpose of the study was to determine some of the quantita- 

 tive relations between climatic conditions and plant growth in terms 

 of the growth rates of a standard plant, as a measure of the effective- 

 ness of the surroundings to produce growth. A further object was to 

 compare the value of various methods of growth determination from 

 the standpoint of their reliable quantitative expression of climatic 

 differences. 



Soy beans up to one month old, from date of sowing, started at 

 intervals of two weeks, were used. They were planted in plunged pots, 

 the same soil being used for all stations. Auto-irrigators were used, 

 thus removing the influence of rainfall. Air temperatures (daily maxi- 

 mum and minimum), evaporation (using cylindrical porous cups), 

 and sunshine were the climatic factors studied. 



Two weeks after planting measurements were taken of stem height, 

 average number of leaves per plant, average length and width of mature 

 leaves, and average of the products of length times width for each leaf. 



At the end of a month these measurements were repeated and the 

 average leaf area and the average dry weight of tops per plant was 

 determined. Work was continued during almost the entire frostless 

 period, comparing Easton, a point close to sea level on Chesapeake 

 Bay, with Oakland in the mountains in the western corner of the State. 



Results. 



1. The total efficiency of the Easton frostless season (200 days) 

 v/as 2.5 times that at Oakland (103 days) measured in terms of leaf 

 product (length and breadth). 



2. Stem height, leaf surface, and dry weight showed greater 

 differences in different periods than did number of leaves and leaf 

 dimensions. Rate of growth in leaf surface and dry weight varied 

 alike, while stem elongation varied in a different proportion with 

 changes in external influences. 



