Spiracle 



One of the external openings of the Trachea (q. v.) of 

 most terrestrial Arthropods. 



Spirochete (Spirochaete) 



A microorganism which moves by undulating its body 

 (not by cilia), parasitic or free-living, classified usually with 

 the bacteria, e.g., the organism causing syphilis. 



Spit 



A long, narrow strip of land extending into the sea, 

 attached to the mainland at one end. 



Splash erosion 



The direct effect of the impact of rain drops on the 

 ground surface or on a thin film of water causing detachment 

 of soil particles which are then readily available for washing 

 away. cf. Erosion, Sheet erosion, gully erosion. 



Sponge 



An animal in the phylum Porifera. 



Spontaneous Generation 



The belief that organisms, even complicated ones, orig- 

 inated directly from non-living substances, cf. Biogenesis. 



Sporangium 



A case-like structure in plants in which spores are 

 produced. 



Spore 



An asexual, Haploid (q. v.), one- or few-celled, reproduc- 

 tive body produced by organisms, cf. Spore-mother cell. 



Spore-mother Cell 



A Diploid (q. v.) cell in plants that gives rise to four 

 Haploid spores. 



Sporophyll 



A leaf or leaf-like structure or scale that produces one 

 or more Sporangia^ e.g., leaves of many ferns, a Stamen. 



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