In This Book, the judgment of the authors, plant biology should always be considered first and human biology last in the course for the following reasons: (1) Plants lend themselves far more readily to close observation and especially to experiments than do animals, and so fundamental processes which apply to all living things can be demonstrated scientifically from plant material. (2) Plants are the final source of all the food supply of animals and man, and if the composition and manufacture of the nutrients are taught early in the course, a solid foundation is laid for all subsequent study of nutrition in animals and man. (3) The purpose of the animal study is largely that of showing the adaptations of animal structure to functions and the relations of the animals studied to human welfare. (4) And finally, if human biology comes last in the course, it may be presented in such a way as to review, sum up, and give real significance to many of the facts learned earlier in the course. In fact, as the work proceeds, comparisons will constantly be made between plants, animals, and man to show that the essential differences in the three kinds of organisms consist not in the differences in the functions which they carry on, but in the organs by which the functions are performed. So far as the order of individual topics under plant, animal, and human biology is concerned, the instructor should plan the sequence that best fits the season. In fact, the last use that a good teacher will make of any laboratory manual or text-book is that of following it slavishly. It is the hope of the authors, however, that the laboratory guides and the text descriptions which follow may be sufficiently suggestive to help some teachers to work out improved methods in biological instruction. In Appendixes I to V, will be found a suggested order of topics which the authors have found satisfactory.