GLOSSARY 441 



Sclerenchyma. A hard tissue with thickened, generally lignified cell walls and non- 

 conductive in function. 



Sclerotium. In myxomycetes, a resting stage in which the Plasmodium becomes a 

 hard waxy mass. In certain higher fungi, a hard compact mass of mycelium con- 

 taining reserve food material. 



Secondaiy xylem. Wood formed by a cambium. 



Sepal. One of the leaf-like parts of the calyx. 



Septate. Divided by walls or partitions. 



Sessile. Without a stalk; attached directly by the base. 



Seta. A slender, bristle-like organ or part, especially the stalk that supports the cap- 

 sule of bryophytes. 



Sieve tube. An elongated living cell in which at least the end walls are perforated, 

 characteristic of phloem tissue. 



Siphonostele. A tubular stele containing a central core of pith. 



Soredium. A special reproductive body of lichens, consisting of a few algal cells sur- 

 rounded by fungal hyphae. 



Sorus. A group or cluster of sporangia, as in ferns. 



Spatulate. Spoon-shaped; gradually narrowed downward from a rounded apex. 



Sperm. A male gamete, generally motile by means of cilia. 



Spermatium. In red algae, a naked, nonmotile male gamete; in certain fungi and 

 lichens, a cell apparently functioning as a male gamete. 



Spermatogenous. Sperm-producing. 



Spermogonium. In certain fungi and lichens, a flask-shaped, sunken receptacle in 

 which spermatia are produced. 



Spike. An inflorescence consisting of sessile flowers borne on a common elongated 

 axis. 



Spirillum. A bacterium that is curved or spiral in form. 



Spongy tissue. The loose parenchyma in a leaf, forming all the mesophyll except the 

 palisade tissue. 



Sporangiophore. A stalk or branch bearing one or more sporangia. 



Sporangium. A cell or organ containing spores. 



Spore. A reproductive body, typically unicellular, capable of direct development into 

 a new individual. 



Sporocarp. A special structure enclosing the sporangia in the water ferns. 



Sporogenous. Capable of producing spores. 



Sporophyll. A spore-bearing leaf, usually more or less modified in form and structure. 



Sporophyte. In plants with an alternation of generations, the individual that bears 

 spores and has the diploid number of chromosomes. 



Stamen. The microsporophyll or pollen-bearing organ of seed plants. 



Stele. The central cylinder in the roots and stems of vascular plants, containing the 

 vascular tissues. 



Sterigma. A slender tip arising from a basidium and bearing a basidiospore. 



Stigma. The portion of a pistil that receives pollen grains and on which they ger- 

 minate. 



Stipule. One of a pair of appendages borne at the base of some leaves. 



Stoma. A small mouth-like opening in the epidermis of a leaf or young stem, bounded 

 by a pair of guard cells, and through which gases pass. 



Strobilus. A compact group of sporophylls borne on a more or less elongated axis; 



a cone. 

 Stroma. A compact, cushion-like mass of mycelium on or in which perithecia are 



borne. 

 Style. The usually attenuated portion of a pistil situated above the ovary. 



