GLOSSARY 251 



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

 are borne ; in Compositos the common receptacle bears the head of 

 flowers, — any structure carrying sexual organs. 



Rhizoid (resembling 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. The growth which takes place in gymnosperms 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 kingdom, 



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 plates 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 egg. 

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

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



Spermogonium. In the rusts a cup-shaped receptacle producing minute 

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



Spindle. A mechanism consisting of delicate fibrils concerned with the 

 distribution of the chromosomes during nuclear division (mitosis). 



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



Spore (seed). A term applied to a variety of one- or few-celled repro- 

 ductive bodies characteristic of groups below the seed plants. 



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



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 plant in an alternation of gen- 

 erations producing asexual spores (see gametophyte). 



Stamen. The pollen-bearing orgjan of seed plants ; 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 polystelic. 



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

 mis) on which the pollen lodges and germinates. 



