384 PLANT STUDIES 



Cotyledon : the first leaf developed by an embryo sporophyte. 



Cyclic : applied to an arrangement of leaves or floral parts in which 



two or more appear upon the axis at the same level, forming a 



cycle, or whorl, or verticil. 



Dehiscence : the opening of an organ to discharge its contents, as in 

 sporangia, pollen-sacs, capsules, etc. 



DicHOTOMOUS : applied to a style of branching in which the tip of the 

 axis forks. 



Dkecious : applied to plants in which the two sex-organs are upon dif- 

 ferent individuals. 



DoRSivENTRAL : applied to a body whose two surfaces are differently 

 exposed, as an ordinary thallus or loaf. 



Egg : the female gamete. 



Embryo : a plant in the earliest stages of its development from the 



spore. 

 Embryo-sac : the megaspore of Spermatophytes, which later contains 



the embryo. 

 Endosperm : the nourishing tissue developed within the embryo-sac, 



and thought to represent the female gametophyte. 

 Entomophilous : applied to flowers or plants which use insects as agents 



of pollination. 

 Epigynous : applied to a flower whose outer parts appear to arise from 



the top of the ovary. 



Fertilization : the union of sperm and egg. 



Filament : the stalk-like part of a stamen. 



Foot : in Bryophytes the part of the sporogoniura imbedded in the 



gametophore ; in Pteridophytes an organ of the spor(jphyte embryo 



to absorb from the gametophyte. 



Gametangium : the organ within which gametes are produced. 

 Gamete : a sexual cell, which by union with another produces a sexual 



spore. 

 Gametophyte : in alternation of generations, the generation which 



bears the sex organs. 



Heterogamous : applied to plants whose pairing gametes are unlike. 



Heterosporous : applied to those higher plants whose sporophyte pro- 

 duces two forms of asexual spores. 



Homosporous : applied to those plants whose sporophyte produces simi- 

 lar asexual spores. 



