Guide to Texas Grasses

Glossary

GLOSSARY A Abaxial. Located on the side away from the axis. Achene. A small, dry, hard, indehiscent, 1-locular , 1-seeded fruit. See caryopsis. Acicular. Needlelike. Acuminate. Gradually tapering to a point. Acute. Sharply pointed, not abruptly or longtapering , but making an angle of less than 90º ; less tapered than acuminate. Adaxial. Located on the side toward the axis. Adnate. Referring to fusion or attachment of unlike structures, such as a palea fused with the lemma. See connate. Adventitious root. A root that arises from any organ other than the primary root or its branches. Adventive. Introduced by chance; referring to accidental seedlings that are imperfectly naturalized. Agrostology. The branch of systematic botany that deals with grasses. Allopatric. Not growing together; occupying different geographic areas; opposite of sympatric . Alpine. Referring to the area above the timberline . Alveolate. Honeycombed, with angular depressions separated by thin partitions. Androecium. The stamens of the flower referred to collectively. Androgynous. Having staminate and pistillate spikelets in the same inflorescence, staminate above the pistillate. Annual. Of one season’s or year’s duration, from seed to maturity and death. Anther. The pollen-bearing part of a stamen. Anthesis. The period during which the flower is open and functional. Antrorse. Directed forward or toward the apex; opposite of retrorse. Apical meristem. Terminal growing point. Apiculate. Terminating abruptly in a small, short point. Appressed. Lying flat or close against something. Arborescent. Treelike in size and habit. Arcuate. Arched or bowed; like an arc. Aristate. Awned; with a stiff bristle at the tip or terminating nerves at the back or margins of organs such as the glumes, lemmas, and paleas. Articulation. A joint or node. See disarticulation. Ascending. Growing obliquely upward, like a culm. Asperous. Rough or harsh to the touch. Asperity. Short macrohair; also termed pricklehair . Asymmetrical. Without symmetry. Attenuate. Tapering gradually to a tip or base. Auricle. An ear-shaped appendage; a structure that occurs in pairs laterally at the base of the leaf blade in some grasses and laterally at the sheath apex in others. Awn. A bristle or stiff, hairlike projection; in the grass spikelet, usually the prolongation of the midnerve or lateral nerves of the glumes, lemmas , or paleas. Axil. The upper angle formed between two structures , such as the leaf or spikelet and stem axis. Axillary. In an axil. Axis. The central stem or branch upon which the parts or organs are arranged, as in the culm or inflorescence. B Basic chromosome number. The lowest, actual or theoretical, haploid chromosome number, designated by x, as x = 7, 9, or 10; usually applied to a group of species. Beaked. Ending in a firm, prolonged, slender tip. Bearded. Bearing stiff, usually long hairs. Bidentate. Having 2 teeth. Bifid. Deeply 2-cleft. Bilobed. Having 2 lobes. Blade. The expanded portion of a flattened structure such as a leaf or flower petal. The 1046 Glossary blade of the grass leaf is the usually flattened, expanded portion above the sheath. Bract. A modified leaf subtending a flower or belonging to an inflorescence; sometimes used in reference to the scales of a vegetative bud or other shoot structure. Bracteal. Of or pertaining to bracts. Bracteate. Having bracts. Bracteole. Small bract. Branch. A division or subdivision of an axis. Bristle. A stiff hair or hairlike projection. Bulb. An underground or partially underground bud with swollen, fleshy scales, such as an onion. Bur. A structure containing seeds and covered with spines or prickles (as in Cenchrus). C Callus. The hard, usually pointed base of the spikelet (as in Heteropogon, Andropogon, and related genera) or of the floret (as in Aristida and Stipa), just above the point of disarticulation . In the former case, the callus is a portion of the rachis; in the latter, it is a portion of the rachilla. In Eriochloa the callus is the thickened node and remnant lower glume; in Chrysopogon it is part of the pedicel. Canescent. With very short white or gray hairs, giving the surface a gray or white appearance. Capillary. As applied to hairs, very slender and fine. Capitate. Head-shaped; collected into a head or dense cluster. Capsule. A dry, more or less dehiscent fruit composed of more than one carpel. Carinate. Keeled with one or more longitudinal ridges. Carpel. A unit of the pistil; a simple pistil is formed from a single carpel and a compound one from 2 or more carpels. Cartilaginous. Firm and tough but flexible; like cartilage. Caryopsis. A dry, hard, indehiscent, 1-seeded fruit with the thin pericarp...