six miles to the Stratosphere (q. v.), in which clouds of 

 moisture form and the temperature decreases with increas- 

 ing altitude. 



Tropotaxis 



The direct orientation of an organism in response to two 

 lights that are moving toward or away from the midpoint 

 between them. cf. Telotaxis. 



True Prairie 



The prairie grassland characterized by tall grasses (five 

 to six or more feet tall) and mid-grasses (two to four feet 

 tall) in the central part of the United States, cf. Pampas. 



Truffle 



Underground fungi in the genus Tuber, class Ascomy- 

 cetes, or their fruiting bodies, edible. 



Truncated Soil Profile 



A Soil profile (q. v.) which has lost part or all of the 

 A and B horizons (q. v.) by accelerated erosion or by 

 cultivation. 



Trypanosome 



A flagellated Protozoan in the genus Trypanosoma, 

 parasitic in the blood of various Vertebrates, and causing 

 serious diseases in man and other animals such as sleeping 

 sickness. 



Tsetse Fly 



A dipterous insect in the genus Glossina, sucks blood and 

 transmits diseases caused by Trypanosomes such as sleeping 

 sickness. 



Tsunami 



A high wave on shore areas, particularly bordering the 

 Pacific Ocean, caused by an earthquake in the ocean floor. 



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