498 PLANTS AND MAN 



Irregular. — A term applied to a flower in which the petals are not all 

 the same size. 



Latex. — The milky juice of a number of plant species, including the 



rubber yielding plants. 

 Legume. — Term applied either to the fruit (pod), or a member, of the 



Pea Family. 

 Lenticels. — The spongy and porous portion of the bark through which 



gaseous exchange takes place. 

 Lignin. — A complex substance associated with cellulose in the cell wall 



structure of plants. 

 Lint. — The long hairs of the cotton seed; used in manufacturing of 



textiles. 



Malt. — The partly germinated grain (usually barley) or its extract, 



used in the brewing of beers and ales. 

 Megaspore. — The large spore developed by seed plant sporophytes, 



germinating into a female gametophyte. 

 Metabolism. — The sum total of all the physical and chemical changes 



taking place in protoplasm during which energy (food) is taken in, 



transformed and utilized. 

 Microspore. — The small spore developed by seed plant sporophytes, 



germinating into a male gametophyte. 

 Monocots (Monocotyledons). — The group of Angiosperms with one 



cotyledon in each embryo; examples, grasses or lilies. 

 Mutant. — An organism exhibiting a mutation. 

 Mutation. — The appearance of a new trait in an off'spring, capable of 



being passed on to the next generation. 

 Multicellular. — A characteristic of body complexity involving many cells 



living in organic continuity with each other. 

 Mycelium. — A mass of hyphae forming the vegetative body of a fungus. 



Naval stores. — Turpentine, rosin and wood tar derived from the sap of 



the longleaf pine. 

 Narcotic. — A drug substance which is used to relieve pain or induce 



sleep. 

 Nitrate bacteria. — Bacteria which can change nitrites to nitrates. 

 Nitrite bacteria. — Bacteria which can change ammonia to nitrites. 

 Jsitrocellulose. — Cellulose which has been "nitrated"; that is, treated 



with any concentration of combined nitric and sulphuric acids. More 



properly called cellulose nitrate. See guncotton and pyroxylin. 



