THE present work is primarily a text-book, but some technical information is included that might more properly be consigned to a reference book. To a considerable extent this reference matter is appended to text paragraphs in the form of notes in smaller type. Although the chief emphasis is placed on Systematic Agrostology, comprising Part II, a brief outline of Economic Agrostology is presented in Part I. In this part the clovers and other forage plants not belonging to the grass family are referred to in classifying the forage plants and their uses. The reader will observe that by the plan adopted the information on a given grass is not found segregated in a single paragraph or chapter but is scattered to meet the necessities of the classification used. The index makes these scattered paragraphs readily accessible. The botanical information concerning each species will be found in the appropriate paragraph in Part II, but the economic information will be found classified in Part I, a part under the chapter on meadow plants, for example, and a part under the chapter on pasture plants. It seems to the author that this method has didactic advantages. In a reference book it might be more convenient to have all the information on one species placed in sequence. Part I is too elementary to meet the demands of a course in agronomy, but it is hoped that it may be found useful as a bridge to connect the subjects of Systematic Agrostology and Agronomic Agrostology.