244 GLOSSARY 



Conjugation. The sexual union of similar gametes to form a zygospore 

 or zygote. 



Cork. Protective tissue in the outer portions of the bark. 



Corm (a trunk). The bulb-like fleshy base of some stems. 



Corolla (a small crown). A collective term for the petals or inner mem- 

 bers of the perianth. 



Cortex. The bark or rind. 



Cotyledon. An embryo leaf borne by the hypocotyl. 



Cuticle (the outer skin). The exterior layer of the epidermis. 



Cystocarp (bladder fruit). The fruit of the red algae resulting from the 

 fertilization of the carpogonium. 



Cytoplasm (cell plasm). The general protoplasm of the cell exclusive of 

 the nucleus and plastids. 



Deciduous (to fall). Falling when their function is performed, as the 



leaves of most hard-wood trees in temperate climates. 

 Dehiscent (to yawn). Opening spontaneously when mature, as anthers, 



to discharge pollen, or as capsules, to discharge spores. 

 Dermatogen (skin producer). The' layer of cells around growing points 



from which the epidermis is derived. 

 Determinate. A term applied to stems where the growth in length is 



determined by the presence of a winter bud, and to an inflorescence 



where there is a terminal flower bud. 

 Diageotropic. Growing horizontally under the influence of gravity, as 



some branches do. 

 Dicotyledonous. Having two seed leaves or cotyledons. 

 Dimorphous flowers (two forms). Flowers which have two forms, as long 



and short styled. 

 Dioecious (two households). Unisexual, the male and female sexual 



organs borne by separate individuals. 

 Dorsiventral (back, belly). Having upper and lower faces, as in most 



leaves. 

 Drupe (an olive). A stone fruit, as a peach or plum. 



Ecology (household discourse). The study of plants in relation to their 

 surroundings. The term is often made to include much of the 

 subject-matter of ecological plant geography, or the distribution of 

 plants on the earth with reference to environment. In this sense 

 it is very frequently used in connection with the study of plant 

 formations. 



Egg. A nonmotile female gamete, generally large in comparison with 

 the sperm. 



Egg apparatus. A group of three cells at the micropylar end of the 

 embryo sac, consisting of the egg and two synergids. 



Elater (a driver). A spirally thickened elongated cell or other filamen- 

 tous structure developed to assist in expelling spores from a spore 



