The text presents an introductory course in plant biology organized in three parts. Part I explains plant physiology, treating protoplasm, absorption, transpiration, conduction, photosynthesis, nutrition, digestion, respiration, growth, and irritability, with emphasis on experimentation and simpler forms. Part II examines morphology and life histories through representative algae, fungi, bryophytes, pteridophytes, gymnosperms, and angiosperms, progressing from simpler to more complex forms to clarify development, reproduction, and fertilization. Part III addresses ecological relationships, tissue organization, organ functions, environmental factors, and plant communities such as forests, prairies, deserts, alpine, and aquatic societies, and includes classification guidance and classroom-oriented pedagogical notes.