Kids Research Express

Stonewort, common name for about 200 species of algae belonging to the phylum Charophyta of the plant kingdom. Stoneworts are so called because the plant surface is usually covered by a thick, brittle, limy crust of calcium carbonate. They are closely related to green algae and have sometimes been regarded as a class (Charophyceae) within that phylum. Stoneworts grow submerged in hard (alkaline) water and often form dense mats on the bottom of ponds and brackish waters. They are much larger than typical green algae and superficially resemble higher plants in their rootlike rhizoids, leaflike branches at regular intervals, and upright cylindrical axes surrounded by a sheath of cells. Asexual reproduction usually involves the shedding of reproductive branches. Sexual reproduction is by the formation, at leaf nodes, of a large egg in a female sexual structure called an oogonium, and of sperm in filaments constituting the male sexual organ, or antheridium.

Deciduous Plants, plants that shed their leaves annually at the approach of a season of cold or drought. The term is also applied to plants that drop leaves, fruits, or flowers at maturity, in contrast to those that retain their foliage or flowers. Plants that keep their foliage throughout the year are called evergreens .

Evergreen, name applied to any plant that retains its foliage through two or more consecutive seasons. In contrast to deciduous plants , which shed their leaves seasonally, evergreens retain their foliage anywhere from 1 to 18 years. Many common varieties, such as spruce , fir , and other members of the pine family, have needle-shaped foliage, but most evergreens are broad-leaved. Some shrubs and trees are both deciduous and evergreen, depending on where they are grown. Many species are valuable for their timber, while mistletoe and other evergreen foliage is popular as Christmas decoration.

Grasses, common name for a large family of flowering plants that is economically and ecologically the most important in the world. The grass family contains about 635 genera and 9000 species, making it the fourth largest family after the legume, orchid, and composite families (see Composite Flowers ). IMPORTANCE All the world’s cereal crops are grasses, and thus the grass family is economically very important. The world’s 5 top crops produce more tonnage than the next 25 combined, and 4 of the top 5 are the cereals rice , wheat , corn , and barley . Human well-being depends on these few grasses, so even small crop failures of any one of them can produce widespread hunger and economic disruption. In addition, the family provides most of the world’s sugar (see Sugarcane ). Another member of the family, bamboo , is an important construction material as well as a food source; it also has been used in papermaking. Citronella, used both in perfumery and as an insect repellent, is an oil

Halophyte, term for salt-resistant plants, coined by the U.S. geologist Oscar E. Meinzer (1876-1948). Found in salt marshes and mangrove swamps, many halophytes could thrive in well-watered lands except for their inability to compete with the other plants found there. Generally fleshy and with gray-green foliage, many halophytes deal with the salt in their environment by eliminating it through special salt-secreting glands in their leaves. Others store the salt in leaves and stems that are shed at the end of the growing season, while the remaining halophytes keep salt from entering their cells by means of semipermeable membranes in their roots. One typical genus is that of the saltbush, Atriplex.

Spices, aromatic flavorings made from parts of plants. The term spice is usually applied to pungent plant products, especially plants native to tropical Asia and the Moluccas, or Spice Islands, of Indonesia. It frequently also includes herbs, which are the fragrant leaves of herbaceous plants, many of which are native to temperate regions. With few exceptions, the spices and herbs known today were being used early in human history. Spice trade with the Orient was flourishing well before the advent of Christianity. The discovery of many spices probably predates the earliest civilizations, when primitive humans were attracted to the aromatic effects produced by what are now called essential oils, which are found in various plant parts. Interestingly, many of the same oils that attracted humans evolved in nature as toxins or repellents against animals; the leaves of the mint plant and the bark of the cinnamon tree, for example, evolved as protection against grass-eating ungulates and bark

The great variety of herb and spice flavors are produced from nearly all parts of plants, from the leaves to the roots. Among those producing fragrant leaves are basil , rosemary , sage , savory, tarragon , and thyme, all of which are small annual or perennial plants. Bayleaf, or sweet laurel , used to flavor meats, sauces, and vinegars, comes from a shrub or tree. Among the many spices derived from the ripe fruit or seeds of plants are aniseed (see Anise ), caraway seed, chili peppers, coriander seed, dillseed (see Dill ), fennel seed, juniper berry, mustard seed, nutmeg, pepper, poppy seed, and sesame seed. Licorice-flavored aniseed, which comes from Pimpinella anisum, a member of the carrot family, is used whole for baking and as an essential oil in candies and the liquors absinthe and anisette. Juniper berry, used to flavor gin, comes from the low evergreen shrub Juniperus communis. The strongest mustard seed comes from black mustard, Brassica nigra, which was probably the