GLOSSARY 739 



Dauermodifikation an experimentally produced modification of the phen- 

 otype in which the effect is attenuated with successive generations until 

 it disappears. 



dCMP deoxycytidine monophosphate. 



dCTP deoxycytidine triphosphate. 



dCTPase an enzyme which degrades dCTP. 



DEAE cellulose dietliylaminoethyl cellulose. 



dedifferentiation reversal of a tissue to a more primitive state; loss of dif- 

 ferentiation. 



dHMP deoxyhydroxymethylcytidine monophosphate. 



dHTP deoxyhydroxymethylcytidine triphosphate. 



diaphysis shaft of long bone. 



differentiation the process of acquiring individual characteristics, such as 

 occurs in the development of the embryo. 



diffusion pressure deficit the pressure difference between two points on a 

 diffusion gradient. 



DNA deoxyribonucleic acid. 



DPA dipicolinic acid. 



Donnan membrane equilibrium equilibrium between the ions of a salt so- 

 lution and the colloidal particles and associated ions of a colloidal elec- 

 trolyte separated by a membrane. 



dTMP thymidine monophosphate. 



dUMP deoxyuridine monophosphate. 



2,4-D 2,4dichlorophenoxyacetic acid. 



ectoblast an embryonic cell layer. 



ectoderm the outermost of the three primary germ layers of the embryo; 

 gives rise to skin, hair, nervous system, etc. 



efficiency index rate of production of new plant material in relation to the 

 dry weight of the plant. 



EMB lactose medium a medium containing eosin, methylene blue, and 

 lactose. 



entropy the theoretical final state of energy equilibrium. 



epharmonic differing from the normal or usual because of influences of the 

 environment. 



epigenesis a theory of embryogenesis which states that development con- 

 sists in the successive formation of new parts which do not preexist in 

 the fertilized embryo. 



epigynous flowers with sepals, petals, and stamens appearing to arise above 

 the ovary. 



epiphysis the head of a long bone; the part of a long bone separated by 

 cartilage. 



euploid an organism whose chromosome number is a whole number mul- 

 tiple of the basic or haploid number. 



fibroblast the connective tissue cells. 



field capacity the moisture content of a well-drained soil after excess has 

 drained away and the rate of downward movement has materially de- 

 creased. 



