The book has been written like a text in other fields is at present not to be found. This book, which has grown out a series of lectures given at all universities is planned to meet the need for a new presentation. Plant physiology is largely a combination of elementary botany, physics, and chemistry. It is, therefore assumed that the student has an elementary knowledge of these contributing sciences. Often a problem of plant physiology can be clarified by material from animal or general physiology can be clarified by material from animal or general crops, horticulturists may lament the lack of horticultural illustrations, and general physiologists may possibly decry the lack of references to work done on the simpler plants and animals, but a book in general plant physiology must be an introduction to do all of its branches; specialization can then follow later.