530 PRACTICAL BOTANY 



Rhizome. See Rootstock. 



Rootstock. A horizontal, more or less thickened, root^like stem, either 

 on the ground or underground. 



Saprophyte. An organism that obtains its food from dead or decay- 

 ing organisms. 



Scalariform (ladder form). A name applied to ducts with piths hori- 

 zontally elongated, and so placed that the intervening thickening ridges 

 appear like the rounds of a ladder. 



Scale (a flight of steps). Any thin scarious body, as a degenerated 

 leaf, or flat hair. 



Sclerenchyma. A tissue composed of cells that are thick-walled, often 

 extremely so. 



Seed. The matured ovule. 



Sepal. A calyx leaf. 



Seta; pi. sets. A bristle, or bristle-shaped body; in mosses, the stalk 

 of the capsule. 



Sexual spore. One formed by the union of cells. 



Sheath. A thin enveloping part, as of a filament, leaf, or resin duct. 



Sieve cells. Cells belonging to the phloem, and characterized by the 

 presence of perforated plates in the wall. 



Sorus (a heap) ; pi. sori. In ferns, the groups of sporangia, constitute 

 ing the so-called " fruit dots " ; in parasitic fungi, well-defined groups 

 of spores, breaking through the epidermis of the host. 



Sperm, or Spermatozoid (animal-like sperm). The male gamete. 



Spermatophytes (seed plants). The highest great group of plants, of 

 which a characteristic structure is the seed. 



Spike. A flower cluster, having its flowers sessile on an elongated 

 axis. 



Spikelet (diminutive of spike). A secondary spike ; in grasses, the 

 ultimate flower cluster, consisting of one or more flowers subtended by 

 a common pair of glumes. 



Sporangium (spore vessel) ; pi. sporangia. The spore-producing 

 structure. 



Spore (seed). Originally used as the analogue of seed in flowerless 

 plants ; now applied to any one-celled or few-celled body which is sepa- 

 rated from the parent for the purpose of reproduction, whether sexually 

 or asexually produced ; the different methods of its production are in- 

 dicated by suitable prefixes. 



Sporogonium (spore offspring) ; pi. sporogonia. The whole structure 

 of the spore-bearing stage of bryophytes. 



Sporophyll. A leaf that bears sporangia. 



Sporophyte (spore plant). The asexual or spore-producing stage of 

 an alternating plant. 



