Marsh Gas 



See Methane. 



Marsupial 



An animal in the subclass Marsupalia, class Mammalia, 

 e.g., kangaroo, opossum. 



Massif 



A principal, relatively uniform mountainous mass with 

 peaks on top. 



Mass Selection 



The choosing of individuals that possess a certain char- 

 acteristic in common from a population such as a corn field, 

 and then bulking the seeds or propagules for later planting. 



Mast 



Nuts such as acorns, beechnuts, and others, in a collective 

 sense, especially when the nuts are used as food for animals. 



Mature Soil 



A soil that is in good adjustment with environmental 

 conditions, in many regions with well-developed horizons, 

 cf. Podzol, Chernozem. 



Meadow 



A grassland, usually in a low, moist area; often mowed 

 for hay. cf. Pasture, Range. 



Mean Sample Tree 



A tree selected for its representative form and that is 

 average hi diameter, height, and volume of the other indi- 

 viduals of the species in a stand. 



Mechanical Analysis 



A laboratory procedure for determining the percentages 

 of clay, silt, and sand in a sample of soil. 



Mediterranean Climate 



The climatic conditions that prevail in lands bordering 



214 



