=Bud variation=: occasionally one bud on a plant will produce a branch differing in some ways from the rest of the branches; this is bud variation. The shoot that is produced by bud variation is called a _sport_. =Calyx=: the outermost row of leaves in a flower. =Cambium=: the growing layer lying between the wood and the bark. =Canon=: the shank bone above the fetlock in the fore and hind legs of a horse. =Carbohydrates=: carbohydrates are foods free from nitrogen. They make up the largest part of all vegetables. Examples are sugar, starch, and cellulose. =Carbolic acid=: a chemical often used to kill or prevent the growth of germs, bacteria, fungi, etc. =Carbon=: a chemical element. Charcoal is nearly pure carbon. =Carbon disulphide=: a chemical used to kill insects. =Carbonic acid gas=: a gas consisting of carbon and oxygen. It is produced by breathing, and whenever carbon is burned. It is the source of the carbon in plants. =Cereal=: the name given to grasses that are raised for the food contained in their seeds, such as corn, wheat, rice. =Cobalt=: a poisonous chemical used to kill insects. =Cocoon=: the case made by an insect to contain its larva or pupa. =Commercial fertilizer=: an enriching plant food bought to improve soil. =Compact=: a soil is said to be compact when the particles are closely packed. =Concentrated=: when applied to food the word means that it contains much feeding value in small bulk. =Contagious=: a disease is said to be contagious when it can be spread or carried from one individual to another. =Cross=: the result of breeding two varieties of plant together. =Cross pollination=: the pollination of a flower by pollen brought from a flower on some other plant. =Croup=: the top of the hips. =Culture=: the art of preparing ground for seed and raising crops by tillage. =Curb disease=: a swelling on the back part of the hind leg of a horse just behind the lowest part of the hock joint. It generally causes lameness. =Curculio=: a kind of beetle or weevil. =Dendrolene=: a patented substance used for catching cankerworms. =Digestion=: the act by which food is prepared by the juices of the body to be used by the blood. =Dormant=: a word used to describe sleeping or resting bodies,--bodies not in a state of activity. =Drainage=: the process by which an excess of water is removed from the land by ditches, terraces, or tiles. =Element=: a substance that cannot be divided into simpler substances. =Ensilage=: green foods preserved in a silo. =Evaporate=: to pass off in vapor, as a fluid often does; to change from a solid or liquid state into vapor, usually by heat. =Exhaustion=: the state in which strength, power, and force have been lost. When applied to land, the word means that land has lost its power to produce well. =Fermentation=: a chemical change produced by bacteria, yeast, etc. A common example of fermentation is the change of cider into vinegar.