The seed, like the ovule of which it is the fertilized and matured state, consists of a nucleus, usually enclosed within two integuments. The outer integument or proper seed coat is variously termed the episterm, spermoderm, or testa.

An annual plant is one which springs from the seed, flowers and dies the same year.

A biennial plant, such as the radish, carrot, beet, etc., does not flower the first season.

A perennial plant is one not absolutely depending upon the stock of the previous season, but annually produces new roots and new accumulations.