GLOSSARY 



66 1 



what thickened or, less commonly, 

 membranous. 



Procambial strand, the meristematic 

 tissue that later develops as vascular 

 tissue; more exactly, a provascular 

 strand. 



Procumbent, lying along the ground. 



Proembryo, applied to the initial stages 

 in embryogeny. 



Prosenchyma, a tissue in which the 

 cells are elongated and tapered. 



Protoderm, the layer or histogen from 

 which the epidermis is derived; der- 

 matogen. 



Protophloem, the first elements of 

 primary phloem to be differentiated. 



Protoplast, the cytoplasm and nucleus 

 of a cell. 



Protostele, a solid stele with phloem 

 surrounding a central core of xylem. 



Protoxylem, the first elements of pri- 

 mary xylem to be differentiated, char- 

 acterized by annular, spiral, or retic- 

 ulate secondary walls. 



Pubescent, covered with soft hairs. 



Raceme, a simple indeterminate flower 

 cluster with a central axis that is more 

 or less elongated. 



R ACHILLA, a secondary axis in the in- 

 florescence of grasses; the axis of a 

 spikelet. 



Rachis, the axis of a spike. 



Radicle, the hypocotyl and rudimen- 

 tary root of the embryo. 



Raphe, the ridge of an ovule extending 

 from the hilum to the chalaza. 



Ray, (of flowers) the branch of an 

 umbel; the marginal flowers in 

 radiate composites; (of axes) radially 

 oriented sheets of cells, i.e., medul- 

 lary, xylem, and phloem rays. 



Receptacle, the portion of the axis 

 from which the floral parts arise; the 

 torus. 



Reniform, kidney-shaped. 



Reticulate, in the form of a network. 



Rhaphe, see Raphe. 



Rhizome, a subterranean stem from 

 which shoots and adventitious roots 

 may arise; a root-stalk. 



Root cap, the protective structure 

 surrounding the terminal meristem 

 of the root, consisting of cells de- 

 rived from the calyptrogen; the 

 calyptra. 



RooT-sTALK, see Rhizome. 



Sagittate, arrow-shaped. 



Samara, an indehiscent winged fruit; a 

 key fruit. 



Scalariform, (of xylem elements) with 

 ladder-like secondary wall thicken- 

 ings. 



Scape, a leafless floral axis arising from 

 the ground. 



ScARious, thin, dry, and membrana- 

 ceous, not green. 



ScHizocARP, a fruit derived from a com- 

 pound pistil in which the one-seeded 

 carpels separate from one another at 

 maturity. 



ScHizoGENOus, applied to a cavity 

 formed by the splitting of cell walls 

 along the middle lamellae. Cf. 

 Lysigenous. 



ScLERENCHYMA, Supporting or protective 

 tissue in which the cells have hard, 

 lignified walls and usually little pro- 

 toplasmic contents at maturity. 



ScuTELLUM, the cotyledon of an embryo 

 of a grass. 



Seed, (in angiosperms) an embryo or 

 embryos with or without an external 

 food reserve, surrounded by a covering 

 which is generally integumentary. 



Seminal, relating to the seed. 



Sepal, one of the members of the calyx. 



Septate, divided by partitions. 



Septicidal, dehiscence of the ovary 

 along the septa between the locules. 

 Cf. Loculicidal. 



Serrate, with sharp teeth. 



Sessile, without a stalk. 



