BOOKS AND CURRENT LITERATURE 



Climatic Conditions as Related to Plant Growth. — The re- 

 cently published work of McLean^ marks a new departure in the pre- 

 cise experimental study of a subject which has heretofore been treated 

 ma nly by general statistical methods. Nine stations were selected 

 in different parts of Maryland, each possessing a ong series of climato- 

 logical observations. Four plants were grown at each of these stations 

 and subjected to accurate growth measurement. The soil conditions 

 were made uniform for all of the cultures by transporting Norfolk 

 sand for use at each station. The soil moisture was maintained at a 

 continuous optimum in the pots by use of the auto-irrigator. The 

 regular meteorological observations were supplemented by readings 

 of evaporation from the porous cup atmometer. Each culture was 

 allowed to grow for four weeks, being measured as to size and leaf 

 area at the end of the first fortnight, and similarly measured at the 

 close of the second fortnight, together with a determination of the 

 dry weight. 



The- data which have been published relate only to the growth of 

 soy-bean at two of the stations — Easton, located at an elevation of 

 32 feet on the Delaware-Chesapeake peninsula, and Oakland, at an 

 elevation of 2500 feet on the Allegheny plateau. The length of the 

 growing season employed at Easton was 171 days and that at Oakland 

 103 days. For the first fortnight of growth the Easton climate pro- 

 duced a mean leaf area which was 33.3 % greater than that secured at 

 Oakland. When the length of the growing seasons is taken into ac- 

 count the efficiency of the Easton climate is 2.21 times that of the 

 Oakland climate. The published data make it possible to correlate 

 each of the five growth criteria with each of the climatological elements 

 a,nd with such derived climatic features as the ratio of rainfall to evap- 

 oration, sums of effective temperature, etc. All of the growth cri- 

 teria exhibit a seasonal march from low values to mid-summer maxima, 

 falling again in the latter part of the growing season. The last fort- 

 nightly period at Oakland exhibited higher temperature and greater 



^McLean, Forman T., A Preliminary Study of Climatic Conditions in Mary- 

 land, as Related to Plant Growth. Physiol. Res. 2: 129-208 (No. 4), 1917. 



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