GLOSSARY 497 



Gamete. — A sexual reproductive cell which must fuse with another 

 gamete before developing into an embryo. 



Gametophyte. — The plant generation reproducing sexually by gametes. 



Genus. — ^A classification unit; a group of related species. 



Glucose. — ^A simple sugar, the most common fuel substance of organisms. 



Guncotton. — Cellulose which has been treated with strong nitric and 

 sulphuric acids; sometimes called "nitrocellulose." 



Gymnosperms. — ^The group of seed plants reproducing by cones or struc- 

 tures with unprotected ovules, and lacking true fruits. 



Habit. — The general appearance of a plant. 



Habitat. — The natural environment in which a plant is found; the kind 



of place in which it lives. 

 Haustorium (pi. haustoria). — ^A finger-like projection from a fungous 



filament into a host cell for purposes of absorbing food. 

 Head. — A type of inflorescence in which many small flowers are all 



attached at practically the same point; example, daisy or dandelion. 

 Heartwood. — The inner woody core of the tree trunk, generally of a 



darker color than the sap wood. 

 Herbaceous. — Characterized by soft stems which die to the ground at the 



end of the growing season; example, buttercup or corn. 

 Herbivorous. — Eating plants as food. 



Heterotrophic. — Pertaining to organisms or metabolism which is depend- 

 ent upon organic material as food, which is either absorbed (fungi) 



or ingested (animals). 

 Humus. — Accumulated debris of plant stems, leaves and roots forming 



the organic material in soil. 

 Hybrid. — ^The type of plant resulting from hybridization. 

 Hybridization. — Crossing two species by transferring the pollen from 



one to the pistil of the other; usually successful only with species of 



the same genus. 

 Hypha (pi. hyphae). — ^A fine, thread-like filament which makes up the 



vegetative part of fungus plants. 



Immunity. — Condition of being able to resist the attack of a disease. 

 Inflorescence. — A cluster or group of flowers; example, yarrow or golden 



rod. 

 Inner bark. — The layer of bark immediately surrounding the cambium 



layer in trees. 

 Invertebrate. — One of a group of animals characterized by no skeleton 



or an external one; example, sponge, jelly-fish, clam or insect. 



