32 



MISC. PUBLICATION 110, U. S. DEPT. OF AGRICULTURE 



synonymous with subgenus. In very 

 large genera the section is often a 

 division of the subgenus. 



Secund : Borne on one side of an axis ; 

 1-sided, as the inflorescence of blue 

 grama. The 

 same as mono- 

 stichous. 



Seed : A fertilized 

 and matured 

 ovule ; the em- 

 bryo (product 

 of sexual con- 

 jugation) of a 

 flowering plant 

 with all its at- 

 tendant, and 

 matured, enve- 

 lopes. 



Semi- : A prefix 

 (Latin) mean- 

 ing half. 



Sepal: One of the 



separate parts (modified leaves) of 

 the outer and lower series of the 

 floral envelope (perianth) ; a divi- 

 sion of the calyx corresponding to a 

 petal in the corolla. (Fig. 66, A, 6.) 

 Also, though less precisely, one of 

 the more or less fused divisions of 

 a gamosepalous calyx (as the five 

 united sepals of phlox). 



Septate: Provided with one or more 

 partitions (septa), as the septate 

 pods of tickclover, or " beggar-ticks " 

 (Meibomia spp.). 



Septum (pi. -ta) : A partition, as, for 

 example, between the seeds in a pod 

 of the legume (pea) family. 





Figure 65. — Scor- 

 pioid inflores- 

 cence, as in the 

 genus Phacelia 



Figure 66. — A, Floral enve- 

 lopes : a, Petals ; 6, sepals ; 

 B, top of pistil ; a, stigma ; 

 I, style 



Sericeous: Silky; closely covered with 

 fine appressed soft straight hairs of 

 silky texture. 



Serrate: Saw-toothed ; having sharp, 

 forward or upward pointed teeth 

 (serrations, or serratures). (Fig. 

 60, A.) 



Serration, or serrature: A saw-tooth- 

 like projection, or tooth, as on the 

 margin of a leaf; a state or condi- 

 tion of being toothed like a saw. 



Serrulate: Finely or minutely serrate. 



Sessile: Literally sitting, i. e., without 

 a stem or stalk; a sessile leaf is 

 without a petiole, or leafstalk, sit- 

 ting directly on the axis or stem of 

 the plant. For example, the sessile 

 leaves of St. Johnswort; the sessile 

 cones of hemlock ; the sessile an- 

 thers of mistletoe. In a spike all 

 the flowers are sessile. 



Seta (pi. -ae) : A bristle, or stiff thick 

 hair. 



Setaceous: Bristlelike. 



Setose : Bristly ; beset with setae, or 

 bristles. 



Sheath: That portion of a leaf (as in 

 grasses, sedges, and rushes) which 

 envelops the stem (fig. 67, c), the 

 terminal free portion of the leaf 

 being known as the lamina, or blade. 

 A modified petiole. 



Figure 67. — Three parts of a grass ; 

 a>, Culm ; b, blade (or lamina) ; 

 c, sheath 



Shrub: A woody (fruticose or frutes- 

 cent), perennial plant, differing 

 from a perennial herb by its persist- 

 ent and woody stems, and from a 

 tree by its low stature and habit 

 of branching from the base. There 

 is, of course, no hard-and-fast line 

 between herbs and shrubs or be- 

 tween shrubs and trees ; all possible 

 intergradations occur. Under very 

 favorable growth conditions, species 

 of shrubs frequently become trees 

 (arborescent) and vice versa. Also 

 there are a few cases of plants 

 (such as the castor-bean plant, 

 Ricinus) which are herbaceous in 

 temperate climates but shrubby or 

 even arborescent in tropical or sub- 

 tropical regions. 



Sieve tube: A canal or tubular vessel 

 composed of thin-walled cells placed 

 end to end in rows and separated, 

 usually terminally but sometimes 

 laterally, by thin perforated parti- 

 tions called sieve plates. Sieve 



