992 MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



Rhizome. An underground stem; rootstock. The rhizomes of grasses are usually 



slender and creeping. They bear scales at the nodes, the scales sometimes 



remote and inconspicuous (Poa pratensis) , sometimes imbricate and prominent 



(Spartina). Rhizomatous. Having rhizomes or appearing like rhizomes, as 



the base of a decumbent stem. 

 Rosette. A cluster of spreading or radiating basal leaves, as in the overwintering 



stage of Panicum, sect. Dichanthelium. 

 Rudiment. An imperfectly developed organ or part. Rudimentary. Under- 

 developed. Applied also to one or more rudimentary florets at the summit 



of the spikelet of some genera, as Melica, Bouteloua, Chloris. 

 Rugose. Wrinkled. Said especially of the fruit of some species of Panicum and 



allied groups. 

 Saccate. Bag or sac-shaped, as the second glume of Sacciolepis. 

 Scabrous. Rough to the touch. Covered with minute points, teeth, or very 



short stiff hairs. Scaberulous. Minutely scabrous. 

 Scale. The reduced leaves at the base of a shoot. Said especially of the reduced 



or rudimentary leaves on a rhizome. 

 Scarious. Thin, dry, and membranaceous, not green. 

 Secondary. Subordinate; below or less than primary. Said of branches arising 



from primary branches. 

 Secund. One-sided or arranged along one side. 

 Self -pollinated. Pollinated in the bud or by pollen from the same flower. The 



opposite of cross-pollinated. 

 Serrate. Saw-toothed; having sharp teeth. Serrulate. Minutely serrate. 

 Sessile. Without a pedicel or stalk. The opposite of pediceled. Said of blades, 



spikelets, and other organs. 

 Setaceous. Bristlelike. Said especially of slender teeth attenuate to an awn. 

 Sheath. The lower part of a leaf that encloses the stem. 

 Sinuous. Wavy. 

 Smooth. Not rough to the touch. Compare glabrous, without hairs but which 



may be rough to the touch. 

 Spathe. A sheathing bract of the inflorescence found especially in the Andro- 



pogoneae. 

 Spike. An unbranched inflorescence in which the spikelets are sessile on a rachis. 



Spikelike. A dense panicle in which the pedicels and branches are short and 



hidden by the spikelets as in Phleum. 

 Spikelet. The unit of the inflorescence in grasses, consisting of two glumes and 



one or more florets. 

 Spreading. Having an outward direction. Said especially of the branches of 



a panicle when they lie between ascending and the horizontal direction (right 



angles). 

 Squarrose. Spreading or recurved at the tip. Said of the tips of lemmas. 

 Stamen. The part of the flower that bears the pollen. Staminate. Containing 



stamens only. Also applied to an inflorescence or a plant with staminate 



flowers. 

 Sterile. Without pistils. A sterile floret may be staminate or neuter. It 



may even lack a palea, and consist of nothing but a lemma. 

 Stipe. A minute stalk to an organ. Applied especially to a pistil. Also some- 

 times to the prolongation of a rachilla as in Calamagrostis. Stipitate. Having 



a stipe. 

 Stolon. A modified propagating stem above ground creeping and rooting or 



curved over and rooting at the tip. Stoloniferous. Bearing stolons. 

 Stramineous. Straw-colored, pale yellow. 

 Striate. Marked with fine parallel lines or minute ridges. 

 Strict. Stiffly upright. 



Strigose. Rough with stiff hairs; harshly pubescent. 

 Sub-. A prefix to denote somewhat, slightly, or in a less degree; as subacute, 



somewhat acute. 

 Subtend. To be below, as a bract subtends a branch in its axil. 

 Subulate. Awl-shaped. 

 Succulent. Fleshy or juicy. 

 Sulcate. Grooved or furrowed. Said chiefly of stems, sheaths, and slender 



blades. 

 Tawny. Pale brown or dirty yellow. 

 Teeth. Pointed lobes or divisions. 



Terete. Cylindric and slender, as the usual unflattened stems or culms of grasses. 

 Tessellate. The surface marked with square or oblong depressions. 

 Trifid. Divided into three parts as the awns of Aristida, 



