=Nitrification=, the changing of nitrogen into a nitrate.

=Nitrogen=, a gas forming four-fifths of the air. Nitrogen is a very necessary food of plants.

=Organic matter=, substances produced by the growth of plants and animals.

=Osmose=, the movement of fluids through membranes or thin part.i.tions.

=Oxygen=, a gas which forms one-fifth of the air. Its presence is necessary to the life of all green plants and all animals.

=Ovary=, the part of the pistil that bears the developing seeds.

=Ovule=, an immature seed in the ovary.

=Perennial=, living through several years.

=Phosphoric acid=, an important plant food found in phosphates.

=Pistil=, the part of the flower which produces seeds.

=Propagate=, to increase in number.

=Pollen=, the powdery substance produced by stamens.

=Pollination=, the transfer of pollen from stamens to pistils.

=Potash=, an important plant food.

=Pruning=, removing parts of a plant for the good of what remains.

=Retentive=, holding, retaining, said of soil which holds water.

=Reverted=, said of phosphoric acid in the process of becoming insoluble.

=Rotation of crops=, a change of crops in regular order.

=Sap=, the juice or liquid contents of plants.

=Seed bed=, the earth in which seeds are sown.

=Seedling=, a young plant just from the seed. Also a plant raised from a seed in distinction from one produced from a graft or a cutting.

=Sepal=, one of the parts of the calyx.

=Slip=, a cutting placed in water or moist soil or other substance to produce roots and form a new plant.

=Soil=, that part of the earth's crust into which plants send their roots for food and water.

=Stamen=, that part of a flower which bears the pollen.

=Stigma=, the part of the pistil which receives the pollen.

=Stomata=, breathing pores in plants.

=Subsoil=, that part of the soil which lies beneath the soil that is worked with the tillage tools.

=Sap root=, a main root that runs straight down into the soil.

=Tillage=, stirring the soil.

=Transpiration=, the giving off of water from plants.

=Tubercle=, a small nodular growth on the roots of plants.

=Under drainage=, drainage from below.

=Vitality of seeds=, the ability of seeds to grow.