MANUAL OF THE GRASSES OF THE UNITED STATES 991 



Panicle. An inflorescence with a main axis and subdivided branches. It may be 



compact and spikelike (Phleum pratense) or open (Avena sativa). 

 Papery. See chartaceous. 

 Papilla. A minute nipple-shaped projection. 

 Papillose. Bearing papillae. Papillose-pilose. Bearing stiff hairs arising from 



papillae. 

 Pappus. In grasses mentioned under Pappophorum, referring to the awns as 

 forming a pappuslike crown, similar to the pappus in certain species of 

 Compositae. 

 Pectinate. Comblike. Used especially with some species of Bouteloua where the 

 spikelets are set close together, parallel and divergent from the rachis like the 

 teeth of a comb. 

 Pedicel. The stalk of a spikelet. Pedicellate. Having a pedicel. Opposed to 



sessile. 

 Peduncle. The stalk or stem of an inflorescence. Peduncled. Having a peduncle. 

 Pendent. Hanging down. 



Perennial. I asting more than 1 year. Applied to grasses in which the under- 

 ground parts last more than 1 year; and to woody culms to distinguish them 

 from those which die to the ground (herbaceous) even though the underground 

 parts are perennial. 

 Perfect. Applied to flowers having both stamens and pistil. 

 Pericarp. The ripened walls of the ovary when it becomes a fruit. 

 Persistent. Remaining attached, either after other parts have been shed, or 

 for a considerable period. The paleas of certain species of Eragrostis persist 

 after the fall of the lemmas. Also used as the opposite of deciduous. 

 Petiole. The stalk of a leaf blade. Used with the leaves of many bamboos, 

 and with some other broad-leaved species in which the blade contracts into a 

 petiole. Petiolate. Having a petiole. 

 Pilose. Pubescent with soft straight hairs. 

 Pistillate. Applied to flowers bearing pistils only and to an inflorescence or a 



plant with pistillate flowers. 

 Pitted. Marked with small depressions or pits. Applied to the fruit (fertile 

 lemma) of certain species of Olyra. Also applied to the pinhole depression 

 in the glume of certain species of Andropogoneae. 

 Plicate. Folded in plaits lengthwise as the blades of Panicum, sect. Ptycophyl- 



lum. 

 Plumbeous. Lead colored, greenish drab, as the spikelets of Eragrostis cili- 



anensis. 

 Plumose. Feathered, having fine hairs on each side. Said chiefly of awns and 



slender teeth. 

 Proliferous. Bearing buds or bulblets in the inflorescence. Compare bulblets. 

 Pruinose. Having a waxy powdery secretion on the surface. Having a more 



pronounced bloom than when glaucous. 

 Puberulent. Diminutive of pubescent. Minutely pubescent. 

 Pubescent. Covered with hairs. Applied especially when the hairs are short and 



soft. Pubescence. A hairy covering. 

 Pulvinus. The swelling at the base of the branches of some panicles which 



cause them to spread. 

 Pustulose. Blistery, furnished with pustules or irregular raised pimples as in 

 the spikelets of Panicum angustifolium. Not as definitely roughened as 

 papillose. 

 Pyramidal. Pyramid-shaped. Applied sometimes to panicles that are actually 



conical. 

 Pyriform. Pear-shaped. Obovoid with attenuate base. Applied to the shape 



of spikelets. 

 Raceme. An inflorescence in which the spikelets are pediceled on a rachis. 



Racemose. In racemes. 

 Rachilla. A small rachis. Applied especially to the axis of a spikelet. 

 Rachis. The axis of a spike or raceme. 

 Reticulate. In a network. Applied especially to the cross-veining on some 



spikelets, as Panicum fasciculatum. 

 Retrorse. Pointing backward, as the hairs on the sheaths of certain species of 



Bromus. 

 Revolute. Turned or rolled backward from both edges. Said chiefly of blades. 



55974°— 35 63 



