GLOSSARY 447 



Palmate. Arranged like the fingers of a hand ; contrasted with pinnate, 

 Panicle. An open or loose flower cluster; a compound raceme. 

 Parasite. An organism which lives in or upon another organism (the 



host), and obtains some or all of its food from the host. 

 Pedicel. The stalk of each individual flower in a cluster. 

 Peduncle. A flower stalk; used to designate either the stalk of .a 



solitary flower or the common stalk of a cluster. 

 Perennial. A plant which remains alive for more than two years. 

 Perfect. Applied to a flower having both stamens and pistil or pistils. 

 Petal. One of the leaf-like parts of a flower next within the sepals. 



Some flowers have no petals ; if present, they are usually the most 



conspicuous parts of the flower. 

 Pinnate. Arranged like the parts of a feather ; applied to the veins or 



divisions of a leaf. 

 Pistil. A structure borne in the central part of a flower, consisting of 



one or more carpels. 



Pistillate. Applied to a flower having a pistil or pistils but no stamens, 

 Plumule. The part of an embryo which is above the cotyledons. 

 Pollen. The small bodies (pollen grains) produced in an anther. 

 Pollen sac. A chamber in which pollen grains are formed ; the same as 



a microspore sac; also called an anther sac. 

 Pollen tube. An outgrowth from the germinating pollen grain, by 



means of which the male gametes of a seed plant are 'carried to the 



neighborhood of the egg. 

 Pollination. The falling or depositing of pollen from the anther upon 



the stigma. 

 Primary leaf . The first leaf, or one of the first leaves, formed by an 



embryo ; in seed plants, the same as a seed leaf. 

 Primary root. The first root ; in a seed plant, the primary root develops 



from the lower end of the radicle. 

 Protein. One of a class of very complex substances produced in living 



cells. Proteins are important constituents of all living matter. 

 Protonema. The thread-like vegetative growth produced by the 



germinating spore of a moss. 

 Protoplasm. The total liquid and semi-liquid constituents of a cell; 



everything inside the cell wall. 



Ptomain. One of a class of substances produced by the action of bac- 

 teria in the decomposition of organic substances. Some of the 



ptomains are extremely poisonous. 



Putrefaction. The decay of organic substances, by the action of bac- 

 teria and other minute organisms. The term is especially applied 



to those forms of decay in which offensive, odors are given off. 



