Pistil. One of the essential organs of a flower, consisting usually of stigma, style, 



and ovary, the ovary containing the ovule or ovules. 

 Pistillate. Bearing pistils only. 



Placenta. The structure or tissue in the ovary bearing the ovules. 

 Placentation. Disposition of the ovules on the placentae within the ovary. 

 Plaited. With more or less equal lengthwise folds; plicate. 



Plane. With a flat surface; projected in the manner of a plane from some desig- 

 nated point or level. 

 Plano-convex. Flat on one side and convex on the other. 

 Plicate. Repeatedly folded, usually lengthwise, though not necessarily so; plaited. 



Plicatulate: the diminutive. 

 Plumose. With hairlike branches as in a feather; said of pappus segments and 



sometimes of branched hairs (fig. 741). 

 Pollen. The powdery grains which bear the sperm nuclei and which are contained 



in the anther. 

 Pollinium (pollinia). A mass of coherent pollen grains characteristic of orchids 



and milkweeds (fig. 363). 

 Polygamo-dioecious. Polygamous but chiefly dioecious. 

 Polygamo-monoecious. Polygamous but chiefly monoecious. 

 Polygamous. Having perfect, pistillate, and staminate flowers on an individual 



plant. 

 Polymorphous. Occurring in more than one form. 

 Polypetalous. With many distinct petals. 

 Primocane. The first year's cane (usually without flowers) of Rubus and similar 



genera. 

 Procumbent. Trailing or lying flat, but not rooting. 

 Proliferous. Bearing supplementary structures such as buds or flowers, either in 



an abnormal manner, or in a manner that is normal but from adventitious tis- 

 sues. 

 Prostrate. Prone, said of stems or leaves that lie on the ground. 

 Protandrous. With anthers maturing before the pistils in the same flower. 

 Prothallium (-a). A cellular, usually flat and thalluslike growth, resulting from 



the germination of a spore, upon which are developed sexual organs or new 



plants. 

 Pruinose. Having a waxy secretion forming a powdery covering. 

 Pseudo-. A Greek combining form to denote false. 

 Pteridophyta. The ferns and fern allies. 

 Puberulent. Covered with a pubescence of very fine, short hairs, not densely 



spaced. 

 Pubescent. Hairy; the general term for hairiness (fig. 785). 

 Pulverulent. Dusted as with fine powder. 



Punctate. With depressed dots scattered over the surface. Punctuate. Dotted. 

 Puncticulate. With very fine depressed dots. 

 Punctulate. Marked with small spots. 



Pungent. Having a long, sharp point; or penetrating, as said of an odor. 

 Pustulate hair. Hair with a bulbous base (fig. 786). 

 Putamen. The shell of a nut; the hardened endocarp of stone fruits. 



Quadrate. Four-angled in cross section. 



Raceme. An inflorescence with a single axis, the flowers arranged along it on ped- 

 icels (fig. 788). 

 Racemose. Characterized by having its parts disposed as in a raceme. 

 Rachilla. The axis of a spikelet, bearing the florets in the Gramineae (fig. 83). 



1724 



