MANUAL OF THE GRASSES OF THE UNITED STATES 987 



Williams, T. A. (1865-1900). Agrostologist, United States Department of 

 Agriculture. Stipa williamsii. 



Willkomm, H. M. (1821-95). German botanist. Willkommia. 



Wolf, John (1821-97). Botanist of Canton, 111., who collected in Illinois and 

 Colorado. Poa wolfii; Trisetum wolfii. 



Wright, Charles (1811-85). Botanist, who collected in Texas and New 

 Mexico, and in Cuba. Andropogon wrightii; Aristida wrightii; Muhlenbergia 

 wrightii; Panicum wrightianum; Pappophorum wrightii; Sporobolus wrightii 



Zois, Karl von (1756-1800). German botanist. Zoysia. 



GLOSSARY 



Abortive. Imperfectly developed. 



Acuminate. Gradually tapering to a sharp point. Compare acute. 



Acute. Sharp-pointed, but less tapering than acuminate. 



Aggregate. Collected together in tufts, groups, or bunches. Applied especially 



to inflorescences. The racemes are aggregate in several species of Andropogon. 

 Annual. Within 1 year. Applied to grasses which do not live more than 1 year. 



Winter annual. A plant which germinates in the fall, lives over winter, and 



produces its seed the following spring, after which it dies. 

 Anthesis. The period during which a flower is open. In grasses, when the 



lemma and palea are expanded and the anthers and stigmas are mature. 

 Antrorse. Directed upwards or forwards. Applied especially to scabrous or 



pubescent stems, sheaths, awns, and so on. Opposed to retrorse. 

 Apiculate. Having a minute pointed tip. Applied especially to fertile lemmas 



in fruit, such as certain species of Eriochloa. 

 Appressed. Lying against an organ. The branches of an inflorescence may be 



appressed to the main axis or the hairs on a stem may be appressed to the 



surface. 

 Aristate. Awned; provided with a bristle at the end, rarely to the back or edge, 



of an organ. In grasses applies especially to the awns at the end of the bracts 



of the spikelet. Compare awn. Aristulate. Bearing a short awn. 

 Articulate. Jointed. Joined by a line of demarcation between two parts which 



at maturity separate by a clean-cut scar. Certain spikelets are articulate 



with the pedicel; certain awns with the lemma. Articulation. The point of 



union of two articulate organs. 

 Ascending. Sloping upward. Applied to stems which curve upward from the 



base, to the branches of an inflorescence which slope upward at angle of about 



40 to 70, and to other parts such as blades and hairs. Compare appressed 



and spreading. 



Attenuate. Gradually narrowed to a slender apex or base. 

 Auricle. An ear. Applied to earlike lobes at the base of blades and to the 



small lobes at the summit of the sheath in tiordeae. Auriculate. Provided 



with ears. 

 Awn. A slender bristle at the end (rarely on the back or edge), of an organ. 



In grasses the awn is usually a continuation of the midnerve (sometimes also 



of the lateral nerves) of the glumes or lemmas, rarely of the palea. 

 Axil. The angle between an organ and its axis. Applied especially to the angle 



between a leaf and its stem and between a branch or pedicel and its axis. 



Axillary. Growing in an axil. 

 Axis. The main stem of an inflorescence, especially of a panicle. Compare 



rachis. 



Barbed. Furnished with retrorse projections. Applied to the spines of Cenchrus. 

 Beak. A hard point or projection. Applied to seeds and fruits. 

 Bearded. Furnished with long stiff hairs, as the nodes of Andropogon barbinodis t 



the callus of Stipa spartea, the throat of the sheath of Sporobolus cryptandrus, 



and the main axils of the inflorescence of Eragrostis spectabilis. 

 Bifid. Two-cleft or two-lobed, applied to the summit of glumes, lemmas, and 



paleas. The lemmas of Bromus are usually bifid at apex. 

 Blade. The part of a leaf above the sheath. 

 Bract. The reduced leaves of the inflorescence and upper part of a shoot. 



Compare scale. 

 Branch. A lateral stem. Applied to the foliage stems or culms, and to the 



lateral stems of an inflorescence. Branchlet. A branch of the second or 



higher order. 



In open much-branched panicles the main branches from the axis are branches 



of the first order, the branchlets from these are branches of the second order 



and so on. 



