GLOSSARY 251 



Receptacle. The extremity of the flower stalk, on which tin- floral parts 

 are borne ; in (.'oiuposltte the cojiimon receptacle hears the head of 

 flowers, — any .structure carrying sexual organs. 



Rhizoid (reseniMing a root). A root-like filament in the lower plants. 



Rootstock. A somewhat root-like stem, usually nearly horizontal and 

 dorsiventral, extending either above or under ground. 



Saprophyte (rotten plant). A plant that lives on dead organic matter. 



Scape (a stem). A leafless peduncle arising from the ground. 



Sclereid (hard). See Stone cell. 



Sclerenchyma. Rigid or strengthening tissue, composed of thick-walled 

 cells, often having the form of fibers. 



Secondary growth. Tlie growth w hich takes place in gymnos]»erms and 

 woody dicotyledons from the development of the cambium cylinder. 



Seed. The fertilized and matured ovule. 



Seed plant. A member of the highest division of the plant king<l«»m, 

 characterized by producing seeds. 



Sepal (a covering). A leaf of the calyx. 



Sieve tubes, or Sieve cells. Soft bast or phloem cells with ] perforated 

 sieve platen in their walls. 



Species. A kind of plant or animal, one of the taxonomic subdivisions 

 of a genus. 



Sperm. A male gamete, generally very small and motile in comparison 

 with the eg^. 



Spermatia. Non-motile sperms, as in the red algae. 



Spermatophytes (seed plants). The great group composed of seed 

 plants. 



Spermogonium. In the rusts a cup-shaped receptacle ]>roduciug minute 

 cells (spermatia) believed to be sjierms no longer functional. 



Spindle. A mechanism consisting of delicate fibrils concerned witli the 

 distribution of the chromosomes during nuclear division (mitosis). 



Sporangium (spore vessel). A spore-producing case. 



Spore (seed). A term ai)plied to a variety of one- or few-celled repri>- 

 ductive bodies characteristic of groups below the seed ]tlants. 



Sporidium (diminutive of spore). A spore produced by a jtromycelium. 



Sporogonium (spore offspring). The sporophyte generation of the liver- 

 worts and mosses, sometimes called the fruit. 



Sporophyll (spore leaf). A leaf which bears spores. 



Sporophyte (spore plant). The asexual })lant in an alternation of gen- 

 erations producing asexual spores (see gameto}>hyte). 



Stamen. The pollen-bearing organ of seed j^lants ; morphologically a 

 microsporophyll. 



Stele (a pillar). The central cylinder of a stem or root. Sometimes a 

 stem has more than one plerome strand at the growing point and so 

 develops several cylinders and is called polj/stelir. 



Stigma (a spot or mark). The portion of the pistil (destitute of epider- 

 mis) on which the pollen lodges and germinates. 



