Tetraplotd 



An organism or part of one having four sets of chromo- 

 somes in its nuclei, cf. Haploid, Diploid, Polyploid. 



Texture (Soil) 



The property of the composition of soil that deals with 

 the relative proportions of various sizes of separates or min- 

 eral particles including clay, silt, sand, and gravel, cf. Struc- 

 ture. 



Thai lop hyte 



A plant in any one of the phyla of algae and fungi, for- 

 merly classified in the division Thallophyta. 



Thallus 



A plant body that is not differentiated into leaves, stems, 

 and roots; one- to many-celled, e. g., Thallophytes. 



Thermal Constants 



The sum of Day-degrees (q. v.) of temperature that is re- 

 quired fqr a plant to mature after planting, cf. Temperature 

 summation. 



Thermal Stratification 



The condition of a body of water in which the successive 

 horizontal layers have different temperatures, each layer 

 more or less sharply differentiated from the adjacent ones, 

 the warmest at the top. cf. Epilimnion, Hypolimnion, In- 

 verse stratification, Thermocline. 



Thermal Zone (Belt) 



A well defined area or zone, occurring on some mountain- 

 sides, in which the vegetation is exceptionally free from frost 

 in the spring and fall. 



Thermocline 



The layer in a thermally stratified body of water within 

 which the temperature decreases rapidly with increasing 



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