418 GLOSSARY 



zoa, which appears and disappears with regularity. It is beUeved to be 

 an organ of excretion. 



Corol'la (Lat. corolla, a little crown) : the petals of a flower taken together. 



Cor'puscles (Lat. corpusculum, a little body) : the red enucleated cells and 

 the colorless cells in the blood. 



Cor'tex : a fleshy portion of the root, outside the central cylinder. 



Cotyle'don (Gr. kotyledon, socket) : leaf of an embryo, in a seed. 



Cul'ture : a growth of bacteria or other microorganisms in a prepared nu- 

 trient medium. 



Cy'toplasm (Gr. kytos, a vessel ; plasma, anything formed) : the living sub- 

 stance of the cell outside of the nucleus and inside the cell membrane. 



Den'drites (Gr. dendron, tree) : delicate protoplasmic branched endings of a 

 neuron. 



Der'mis (Gr. derma, skin) : the layer of skin below the epidermis. 



Di'aphragm (Gr. diaphragma, a partition wall) : the muscular partition be- 

 tween the thorax aiid the abdomen. 



Di'astase : an enzyme formed in plants which changes starch to grape sugar. 



Dicotyle'don : a plant that bears seeds having two cotyledons. 



Dififu'sion : the passage of particles of a substance, either gas or liquid, from a 

 point of greater to a point of lesser concentration. 



Diges'tion (Lat. digestio, the dissolving of food) : the process of preparing 

 food for absorption. 



Dihy'brid. Mendelian term for a cross between organisms which differ in 

 two pairs of alternative characters. 



Disease' : a state in which part of the body does not function properly. 



Disinfect'ant : something which kills bacteria. 



Dor'sal (Lat. dorsum, the back) : of or pertaining to the back or top side. 



Ductless glands : glands which have no communication with an outer surface, 

 and which manufacture hormones. 



E 



Ec'todenn (Gr. ectos, outside ; derma, skin) : the outer layer of cells in an 



embryo. 

 Em'bryo (Gr. emhryon, a young one) : the early stage of a developing plant or 



animal. 

 Em'bryo sac : the structure within the ovule which holds the egg cell. 

 Emul'sion (Lat. emulaere, to milk out) : a mixture of liquids which do not 



dissolve, the particles of one floating as small globules in the other. 

 Enam'el : hardest part of a tooth. 



Encysf : to become inclosed in an impermeable envelope or cyst. 

 En'doderm (Gr. endon, within ; derma, skin) : the inner layer of cells in an 



embryo, giving rise to the digestive tract, etc. 



