Therophyte 



One of the classes of life-forms of Raunkiaer that includes 

 the annual plants. 



Thiamine 



A vitamin (Bj) required by numerous organisms, but 

 formed only in green plants and in some microorganisms. 



Thicket 



Vegetation that is dominated by a dense growth of small 



trees and shrubs. 



Thigmotaxis 



The movement of an organism to secure close contact 

 with an object, syn. Stereotaxis. 



Thigmotropism 



The response of a plant or a portion of it to a con- 

 tact stimulus, e.g., a tendril growing around a stem. syn. 

 Stereotropism. 



Thorax 



(1) The part of the body in higher Vertebrates, contain- 

 ing the heart and lungs. (2) The middle portion of the body 

 of insects, bearing the legs and wings (when present). 



Thorn 



A stiff, pointed, modified branch in plants such as the 

 hawthorn. 



Thorn Forest 



A vegetation type in the Tropics or Sub tropics consisting 

 mostly of thorny trees, shrubs, and vines; Xerophytic in 

 aspect, and subject to long droughts. 



Threadworm 



See Nematode. 



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