A similar method of dispersal is employed by the Malagasy plant Uncarina peltata, whose dry fruits, 3 inches in diameter, have numerous long, slender bristles, each terminated by four small, recurved hooks. One of these fruits attached to fur or clothing is very hard to dislodge.

One of the Chinese waterchestnuts (Trapa bicornis) has blackish fruits 3 inches across that closely resemble a bull's head, with two stout, curved, sharp-pointed horns. These fruits float for some distance before sinking to the bottom of the shallow river or pond, where they may germinate.

The dipterocarps (Dipterocarpus), tall trees from tropical Asia, are a source of the commercial gurjun balsam. Their fruits are small and globular and have a persistent calyx. Two of the sepals become greatly elongated up to 7 inches long, and the other three remain short. The elongated, winglike sepals enable the fruits to be wind propelled for long distances.

THE RECEIPT of a shipment of cabbage seed from Russia in February 1898 marked the beginning of a continuing program of plant introduction by the Department of Agriculture, which collects plant materials, mostly as seeds, from all parts of the world for experimental purposes.

The introductions are received from the Department's agricultural explorers, foreign institutions, and other sources. They usually represent special strains or varieties of existing crop plants, or they may be wild relatives of cereals, forage plants, fruit, vegetables, fiber plants, oil-yielding plants, and plants for special projects.

Seeds of weeds may come into the United States with imported crop seeds and on ships and airplanes. Most of the noxious weeds in this country were introduced from foreign sources in this manner. Familiar examples are field bindweed (Convolvulus arvensis) and Canada thistle (Cirsium arvense).

Some kinds of plants that are not important weeds in their native land sometimes become extremely objectionable under certain conditions in parts of this country as, for example, giant foxtail (Setaria faberi) and St. Johns-wort (Hypericum perforatum).

It is highly important therefore that all imported seeds, whether crop or weed, be correctly identified and evaluated before planting.

THE IDENTIFICATION of seeds and seedlike fruits usually is based on external morphological features, such as shape, size, color, and surface configuration or texture. Sometimes the internal anatomy of the seed the size and position of the embryo or the nature of the endosperm, for example furnishes useful clues to its identity.

For seed identification of special groups, particular attention is paid to the features that are characteristic of the group. For example, in determining species of the genus Cucurbita, which includes pumpkins, squashes, and cushaws, special attention is paid to the shape of the hilum (seed scar), the character and color of the seed margin, and the color of the seed face.

The identification of seeds of the genus Phaseolus, the cultivated beans, takes into account the position, shape, and size of the hilum, the nature of the caruncle and micropyle, the nature and color of the seedcoat, and the nature of the parahilum, which is a small area next to the hilum and is characterized by two small tubercules.

Seeds of two species of Hibiscus, the kenaf (H. cannabinus) and the roselle (H. sabdariffa), both of economic importance, are almost alike, except that glossy, pale-brown spots occur on the surface of H. cannabinus.

Seeds of the mimosa family (Mimosaceae) , with one or two exceptions, are easily separated from the seeds of other legumes by a horseshoe-shaped design on the seed faces. A continuous elliptic or oval design on the seed faces would place the seed in the family Caesalpiniaceae.

A SEED HERBARIUM is essential for reference in identifying seeds, since published descriptions of plants rarely include the necessary morphological details of the seed and mature seeds are usually not present on specimens in plant herbariums. Newly introduced plant materials frequently must be identified promptly in order to be handled effectively.

The Department of Agriculture maintains a large general seed herbarium at the Plant Industry Station at Beltsville, Md., consisting not only of seeds, ranging in size up to 2 inches or more in diameter, but also seedlike fruits and certain types of dry fruits. The herbarium is used chiefly for identifying or checking the identification of newly introduced plant materials.

Another large seed herbarium, at the Agricultural Research Center, Beltsville, that consists mostly of actual and potential weeds and seeds of crop plants, is used mainly for identifications in carrying out the provisions of the Federal Seed Act.

Together, these seed herbariums total about 100 thousand samples, which come from all parts of the world. More than 250 plant families are represented, with 17 thousand species.

These herbariums may be used by anyone who cares to consult them.

Some persons have learned that the study of seeds is an absorbing and profitable hobby. It involves little expense and a small amount of time and energy. It is a field in which there are satisfying and practical returns. For the farmer or nurseryman, a collection of seeds of authentically identified plants is of value in checking new or little-known seed materials. The introduction of new and possibly dangerous weeds could very well be forestalled if authentic samples of them were on hand for comparison. Small glass vials and gummed labels from a pharmacy are ideal for filing small samples of seeds.

PAUL G. RUSSELL is a collaborator in the New Crops Research Branch, Agricultural Research Service. Before retiring in 1959, he was a botanist in the same branch.

ALBINA F. MUSIL was a seed technologist in the Seed Branch, Grain Division, before she retired in 1960.