858 Appendix 



Spiracle (spir' a kl) (L. spiraculum, air hole), external opening of respiratory sys- 

 tem of insects. 



Splanchnic (splangk' nik) (Gr. splanchnon, entrail), pertaining to internal, vis- 

 ceral organs. 



Spleen (Gr. splen, spleen), ductless, vascular organ near the stomach. 



Spongin (spun' jin) (Gr. spongos, sponge), horny material allied to silk, forming 

 skeletal fibers of certain sponges, especially commercial types. 



Spongy tissue, plant mesophyll tissue with cells loosely arranged, with many in- 

 tercellular (air) spaces, and located beneath the lower leaf epidermis. 



Spontaneous generation, see Abiogenesis. 



Sporangium (spor -an' jium), structure containing spores. 



Spore (Gr. sporos, seed or spore), cell with resistant covering and for reproductive 

 purposes; one or several may be produced at one time, depending on the 

 species. 



Spore mother cell, a cell which by cell divisions produces usually four spores. 



Sporophyll (spor' o fil) (Gr. spor a, spore; pyllon, leaf), a leaf that bears sporangia. 



Sporophyte (spor'ofite) (Gr. spora, spore; phyta, plant), spore-bearing (asexual) 

 generation in plants exhibiting alteration of generations. 



Sport, a mutant. 



Squamous (skwa'mus) (L. .yq^Mawa, scale), flat, scalelike. 



Stamen (sta'men) (L. sta, stand), pollen-bearing structure of a flower. 



Statocyst (stat' o sist) (Gr. statos, stationary; kystos, sac), organ of equilibrium 

 as in medusae. 



Steapsin (ste -ap' sin) (Gr. stear, tallow; pepsis, digest), a pancreatic enzyme able 

 to change fat to fatty acid and glycerin. 



Stele (ste'le) (Gr. stele, post), central cylinder of united vascular bundles in the 

 root and stem of dicotyledonous seed plants. 



Sterigma (Gr. sterigma, support), a stalk for bearing a basidiospore. 



Sterile (ster' il) (L. sterilis, barren), infertile, free from all types of organisms. 



Sternum (stur' num) (L. sternum, breast bone), breast bone. 



Stigma (stig'ma) (L. stigma, a mark), upper part of pistil to receive pollen; or 

 same as eyespot. 



Stimulus (stim'ulus) (L. stiryiulare, to incite), condition or substance which in- 

 duces a response. 



Stoma (plural, stomata) (stom' a) (Gr. stoma, mouth), small opening as in 

 leaves. 



Striated (stri' a ted) (L. stria, channel), marked by small channels, usually 

 parallel. 



Strobilus (strob' i lus) (Gr. strohilos, twisted), cone-shaped group of sporophylls 

 in horsetails, conifers, etc. 



Style (sti' 1) (Gr. stylos, pillar), stalk to support the stigma. 



Subclavian (sub -kla' vi an) (L. sub, under; clavis, clavicle or collar bone), under 

 the collar bone. 



Subcutaneous (sub ku -ta' ne us) (L. sub, under; cutis, skin), beneath the outer 

 skin. 



Supplemental factors, genes which modify and supplement the ability of other 

 genes. 



Suprarenal (supra -re' nal) (L. supra, above; ren, kidney), an endocrine (duct- 

 less) gland above each kidney (also called adrenal). 



