_monocotyledon._ Having one cotyledon or seed-leaf. _monœcious._ Said of plants that bear the stamens and pistils in different flowers on the same plant. _mycelium._ The vegetative part of a fungus, composed of threads or hyphæ. _mycorrhiza._ A root covered with or bearing a fungus that aids the root in securing nourishment from the soil. _naked._ Said of flowers that lack envelopes (calyx and corolla). _nectary._ A cup, sac, or place in the flower in which nectar (or “honey”) is borne. _osmosis._ The passing or diffusion of liquids or gases through membranes. _ovary._ The lower enlarged part of the pistil, containing the ovules or forming seeds. _ovule._ The young or forming seed. _palmate._ Palm-like; said of venation that arises from the base of the leaf (top of petiole), or of leaflets similarly arranged. _panicle._ A branching raceme. The lower or outer flowers open first; but the word is often used loosely. _pappus._ The hair, plumes, bristles, or scales on the top of a dry fruit, particularly of a fruit (or “seed”) of the Compositæ or sunflower family. _parasite._ A plant or animal that lives on a living host (as on a plant or an animal), taking its food from the host. See _saprophyte_. _parenchyma._ The general underlying tissue, from which other tissue arises. _pedicel._ Stem of a single flower in a cluster. _peduncle._ A flower-stem, supporting a solitary flower or a cluster of flowers. _perennial._ A plant that lives more than two years, as most grasses, docks, alfalfa, asparagus, and all trees and shrubs. _perfect flowers_ bear both stamens and pistils. _pericarp._ A ripened ovary, without counting attached parts. _personate._ Masked; that is, so formed as to suggest a masked face, in labiate corollas with a large lower lip. _petal._ One of the parts or leaves of the corolla. _petiole._ Stem or stalk of a leaf. _petiolule._ Stem of a leaflet. _phenogam_ (_phænogam_, _phanerogam_). A seed-bearing plant; that is, one of the seed-bearing or flowering group of plants. _phloem._ Bark or soft bast tissue. _photosynthesis._ The process whereby the carbon dioxide of the air is appropriated in the formation of material for plant growth. _phyllotaxy._ Mode of arrangement of leaves or flowers on the plant or stem. _pinnate._ Feather-like; said of leaves in which the veins strike off from a continuing midrib, or in which the leaflets are arranged in a similar order. _pistil._ The innermost member in the flower, bearing the forming seeds. _pistillate._ Of pistils only; a flower that contains pistils and no stamens, or a plant that bears only pistils. _plur-annual._ A plant of a tropical or semi-tropical climate that is annual in a colder country only because it is killed by frost; as tomato, castor bean.