In higher plants the meristem tissue in the root and stem tips, in the buds, and in the cambium are areas of active growth. Plants also differ from animals in the internal structure of the cell and in certain details of reproduction. In additional, plants grow continually throughout life and have no maximum size of characterstic form in the adult, as do animals. In these the gametophyte begins life inside an enclosure called a seed, which develops while on the parent plant, and with fertilization by means of pollen grains.
