GLOSSARY 123 



Pellicle (from the Latin, pellicula, the diminutive of pellis, meaning "skin") : a 



thin lifeless membrane about a free-living cell. 

 Periphery (from the Greek, peri, meaning "around," and phiercin, meaning to 

 bear" or "to carry") : the external boundary or superficial parts of any body. 

 Periplast: a lifeless cell membrane, equivalent to "pellicle" (q.v.). 

 Periplasm (adjective, periplastic) ; enclosing or outer protoplasm. 

 Photosynthesis: the process by which carbohydrates are formed from inorganic 



compounds by the chlorophyll of plants in sunlight. 

 Phylogeny : the race history of an animal or a plant type, in distinction from the 



development of the individual organism (ontogeny). 



Phylum (plural, phyla) ; one of the primary divisions of the animal or vegetable 



kingdom, so called because the members are assumed to have a common descent. 



Plastid: (1) a unit of protoplasmic matter: (2) any of certain small bodies of 



specialized protoplasm lying in the cytoplasm {q.v.) of some cells, especially 



plant cells and those of certain protozoa, and serving in many cases as organs 



or places of special activities concerned with metabolism (q.v.). 



Prophylaxis : the art of guarding against, preserving from, or preventing disease ; 



observance of the rules necessary to preserve health. 

 Proteins (from the Greek word, proteuein, meaning "to be first") : any of a class 

 of extremely complex substances which are of first importance in physiological 

 chemistry, being essential constituents of all living cells, both animal and 

 plant, and also of the diet of the animal organism. 

 Proteolysis (adjective, proteolytic) : the hydrolysis (q.v.) of proteins with the 



formation of simpler and soluble products, as occurs in digestion. 

 Protista : the unicellular organisms collectively, including both the one-celled 



animals and the one-celled plants. 

 Protoplasm : the living substance of which animals and plants are essentially 



composed. 

 Protophyte (plural, protophyta ; adjective, protophytic) : an unicellular plant. 

 Protozoan (plural, protozoa ; adjective, protozoan) : a minute animal, generally 

 consisting of a single cell, or of a colony, all the cells of which are funda- 

 mentally alike. 

 Pseudopodium (plural, pseudopodia) : a temporary protrusion or retractile process 

 of the protoplasm of a cell, especially of an unicellular organism. Pseudopodia 

 may have a fairly definite filamentous form, sometimes fusing with others to 

 form a network, or they may be irregularly lobate as in the ameba. They serve 

 various purposes, especially as means of locomotion or for taking up food. 

 Reproduction : the means by which a life-form is continued and multiplied. 

 Reproduction by division : the simplest, or fundamental, form of multiplication. 



In the last analysis all reproduction is by division. 

 Saprophyte (adjective, saprophytic) : a plant living on dead and decaying plants 



or animals. 

 Saprozoic : living on proteins and carbohydrates in solution. 

 Somatella : usually a transient stage in development in which the nucleus has 



divided several times, while the cell body remains undivided. 

 Sporoblast: in certain protozoa (the sporozoa), a cell which divides into 



sporozoites (q.v.). 

 Sporozoite: in sporozoa.^ a small active, usually elongate, spore, especially one of 

 those produced by division of the sporoblasts (q.v.) into which the zygote 

 divides. 

 Sporulation : the division into many small spores, especially after encystment. 

 Staining: a complicated process for the purpose of coloring certain parts of 



the cell (e.g., the nucleus). 

 Symbiosis _ (adjective, symbiotic) : the living together in more or less intimate 

 association or even close union of two dissimilar organisms. Ordinarily the 

 term is used in cases where the association is advantageous (often necessary) 

 to one or both, and not harmful to either. 

 Swarmer: a spore with the ability to move independently, usuallv by means of 



flagella. 

 Synthesizing: the putting of two or more elements or simple compounds together 



to make a new compound ; the opposite of analvzing. 

 Thallophytes : plants of very diverse habits and structures, including the algae, 

 the fungi, and the lichens. 



