GLOSSARY 445 



Endosperm. The food-containing tissue lying outside the embryo and 



within the seed coat. 

 Enzym. A substance produced in a Hving cell which causes or hastens 



particular chemical changes in other substances. 

 Epidermis. The outer layer of cells of leaves, stems, roots, or fruits. 

 Epiphyte. A plant which grows, usually at some distance above the 



ground, upon another plant but not parasitic upon it. 



Family. A group of related genera. 



Fermentation. Any one of many chemical changes produced by simple 



organisms such as yeasts or bacteria ; especially, but not exclusively, 



those in which bubbles of gas are given off. 

 Fertilization. The union of unlike male and female gametes. 

 Fiber. An elongated, usually slender cell with firm walls ; as bast 



fibers or wood fibers. 

 Filament. The stalk-like part of a stamen below the anther. 

 Fruit. A ripened ovary with the seed or seeds inclosed within it. 

 Fungus. A comparatively simple organism which contains no chlo- 



rophyl. 



Gamete. A cell which may unite with another cell, thus forming a 



Genus. A group of related species. 



Germinate. To begin to grow, usually after being for some time in a 

 resting or dormant condition ; applied to spores, zygotes, and seeds. 



Gill. One of the vertical flaps on the under side of the cap of a mush- 

 room, on whose surface spores are borne. 



Glandular. Applied to a structure whose function is the secretion of 

 some special substance. 



Grafting. The attachment of the parts of two plants in such a way that 

 they will grow together. 



Head. A dense cluster of flowers on a very short axis. 



Heartwood. The hard inner layers of the wood of the trunk and larger 



branches of a tree or shrub. Distinguished from sapwood. 

 Host. An organism (plant or animal) on or in whose tissues a parasitic 



organism lives. 

 Hybrid. A plant produced by the crossing of two species or varieties. 



Imperfect. Applied to a flower having either stamens and no pistil, 



or a pistil (or pistils) and no stamens. 

 Infection. The establishment of a parasite in or upon the tissues of a 



host, 



