The word weed has been defined in many different ways. A fairly comprehensive definition is the following: "A weed is a plant which grows where it is not wanted;" in other words, "an undesirable plant citizen. " A plant may be a weed at one time and useful at some other time, depending upon its environment. For instance, a wheat plant may appear in the cornfield. It is then a weed. Then again one corn plant may be a weed to another corn plant. For instance, if eight plants come up in a hill where only three are desired, five of these plants are really weeds. This, then, is the broad conception of the term weed. KINDS OF WEEDSWeeds may be classified in different ways. One of the most useful classifications is based on the length of time the weeds live. This gives three classes: (1) annual, (2) biennial, and (3) perennial.An annual weed is one that starts from the seed in the spring, develops into a plant which flowers and seeds the same year, and then dies; or, in other words, an annual weed is one that lives but one growing season. Most of our weeds belong to this class. It includes wild mustard, foxtail, wild oats, pigweed, Russian thistle, corn cockle, kinghead, ragweed, and many others. Some plants are known as winter annuals. Their seeds ripen early in the summer, fall to the ground and germinate, reaching a certain stage of growth before frost. As soon as the frost is out of the ground the next spring, they continue their growth and ripen seeds very early in the spring. Such plants are, in a sense, biennial in their habits, though not real biennials. Some weed examples of winter annuals are French weed, peppergrass. and shepherd's purse. These plants are also annuals, however, just as winter wheat is a winter annual, but, if sown in spring, is an ordinary annual. Note.-In this bulletin the terminology in regard to seeds and fruit is that of the farm and seed trade. For instance, a Canada thistle "seed" is in reality a fruit. Adhering to the strictly accurate botanical terminology leads only to confusion and complexity in a bulletin intended for practical farm use. The term pod is used in the common sense of a capsular fruit, and not necessarily to designate a legume. The drawings in this bulletin are all original. The drawings of seedlings were made by E. W. Norcross and G. D. George, those of mature plants by G. D. George, and those of seeds by F. H. Hillman.