364 American Midland Naturalist Monograph No. 7 



Pinna. A primary division of a pinnate leaf. 



Pinnate (leaf). Compound, with the leaflets on each side of a common 



petiole or rachis. 

 Pinnatifid. Cleft or divided in a pinnate manner, the sinuses or lobes 



narrow or acute. 

 Pinnule. One of the smaller subdivisions of the primary divisions of a com- 

 pound leaf, especially of ferns. 

 Pistil. The ovule-bearing part of a flower, comprising ovary, style, and 



stigma; consisting of a single carpel (simple pistil) or of two or more 



partly or wholly fused carpels (compound pistil). 

 Pistillate flower. A flower with a pistil but no stamens. 

 Placenta. Any part of the interior of the ovary which bears the ovules. 

 Plano-convex. Plane on one side and con\ex on the other. 

 Plicate. Folded like a fan. 

 Plumose. Featherv-; furnished with long hairs as the beak of the achene 



in Clematis, or the pappus of some Compositae. 

 Pollen. Microspores, or partially developed male gametophytes, formed in 



the anthers of seed plants; the powdery contents of an anther. 

 Polygamous. Bearing unisexual and bise.xual flowers on the same plant. 

 PoLYPETALOUs. With petals separate. 

 Pome. An accessory fruit composed of the pericarp and enlarged receptacle, 



as in the apple. 

 Prickle. A sharp-pointed outgrowth of the cortex and epidermis of a stem 



or leaf, as in rose, blackberry, etc. 

 Primocane. a biennial stem in its first (vegetative) season. (Rubus). 

 Procumbent (stem). Trailing on the ground, but not rooting at the nodes. 

 Proliferous. Producing offshoots, sometimes abnormal, as when carpels 



or stamens give rise to leafy shoots. 

 Prostrate. Lying flat on the ground. 

 PuBERULENT. Minutely pubescent. 



Pubescent. Covered with pubescence, an indument of hairs (trichomes). 

 Pulverulent. Appearing as if covered with powder or dust. 

 Punctate. Marked with small dots or translucent glands. 

 PuNCTicuLATE. Minutely punctate. 



Pungent. Terminating in a rigid sharp point; also of acrid flavor. 

 Pyriform. Pear-shaped. 



QuADRiFOLiATE. Four-lcavcd. 

 Quadrifoliolate. Having four leaflets. 



Raceme. An indeterminate inflorescence with pedicellate flowers on a more 



or less elongated a.xis. 

 Racemose. In a raceme, or resembling a raceme. 

 Rachilla. a secondary axis or rachis; in the grasses and sedges the axis that 



bears the flowers. 

 Rachis. An axis bearing flowers or leaflets. 

 Radiate. Spreading from a common center; in the Compositae, a head with 



ray-flowers. 

 Ray. The branch of an umbel; the marginal flowers (ray-flowers) of an 



inflorescence if diflferentiated ; the strap-shaped part of the corolla of 



the ray-flowers in Compositae. 

 Receptacle. The more or less expanded portion of an axis bearing the 



organs of a flower or the collected flowers of a head. 



