Joseph Parente, age 10, of West Warwick, R.I., for his question:

What are monocots and dicots?

Monocots and dicots are flowering plants, but no one can say whether the most beautiful blossoms bloom on monocots or dicots. The glamorous orchid is a monocot, and the lovely rose grows on a dicot plant. On the other hand, both types also produce small and un noticeable flowers. Pea blossoms are dicots, and little green grass flowers are monocots.

Our green world is embroidered with about 250,000 different varieties of flowering plants. These most advanced members of the vegetable kingdom are classified as angiosperms, meaning plants that shelter their seeds in protective coats, and in the long history of green plants they were the latest arrivals. The gorgeous army of flowering plants is divided into two subclasses, the monocotyledons and the dicotyledons. These long words were shortened by the experts to monocots and dicots.

You can tell that the oak tree is a dicot by examining its leaves and its woody trunk. The ridged veins of its leaves crisscross in networks. The woody cells of its trunk and trigs grow in a series of circles, one outside another. You can tell that the wild rose is a dicot, because its pastel pink petals grow in fives. You can tell that the stately daylily is a monocot, because its veins grow along its long leaves in parallel lines and its graceful flowers bear six petals.

There are some 200,000 different dicots, and most of them do their growing from a circle of special cambium cells. There is a circle of cambium around the trunk of the oak tree under the bark. Every year it adds cells to the bark and a ring of new woody tissue around the trunk. The cambium cells of the dicots circle twigs and trunks, stems and stalks. Most dicots have networks of veins and most have flower parts in series of fours or fives.

The monocots have no cambium cells, and most of them cannot add new growth from year to year. Their long veins usually run in parallel lines, and their flower parts grow in threes and sixes. Iribes and daffodils are monocots; so are the cereals and the grasses. The palms and bamboos are monocots, but most of our trees, shrubs, bushes and other garden plants are dicots.

Cotyledons are the meaty seed leaves that store food for the embryo seed. The dicots have two cotyledons, the monocots only one. A fat lima bean is made up mostly of two cotyledons that can be pried apart. If the bean is allowed to grow, the embryo seed between the cotyledons will sprout a root and a shoot. The cotyledons will turn into the first pair of green leaves and produce food for the baby seedling. The one cotyledon of a monocot does not become a food producing leaf.