I have pleasure in acknowledging my indebtedness to the following works for illustrations which are inserted by permission of the several publishers:--Stebler’s _Forage Plants_ (published by Nutt & Co.), Nobbe’s _Handbuch der Samenkunde_ (Wiegandt, Hempel and Parey, Berlin), Harz’s _Landwirthschaftliche Samenkunde_ (Paul Parey, Berlin), Strasburger and Noll’s _Text-Book of Botany_ (Macmillan & Co.), Figuier’s _Vegetable World_ (Cassell & Co.), Lubbock’s _Flowers, Fruits and Seeds_ (Macmillan & Co.), Kerner’s _Natural History of Plants_ (Blackie & Son), and Oliver’s _First Book of Indian Botany_ (Macmillan & Co.). It is impossible to avoid the question of variation in work of this kind, and students will without doubt come across instances--especially in such genera as _Agropyrum_, _Festuca_, _Agrostis_ and _Bromus_--of small variations which show how impossible it is to fit the facts of living organisms into the rigid frames of classification. It may possibly be urged that this invalidates all attempts at such classifications: the same argument applies to all our systems, though it is perhaps less disastrous to the best Natural Systems which attempt to take in large groups of facts, than to artificial systems selected for special purposes. Perhaps something useful may be learned by showing more clearly where and how grasses vary, and I hope that the application to them of these preliminary tests may elucidate more facts as we proceed. H. M. W. CAMBRIDGE, _April_, 1901. CONTENTS. CHAPTER I. PAGE THE VEGETATIVE ORGANS 1 CHAPTER II. THE VEGETATIVE ORGANS (_continued_) 17 CHAPTER III. GRASSES CLASSIFIED ACCORDING TO THEIR VEGETATIVE CHARACTERS 39 CHAPTER IV. ANATOMY AND HISTOLOGY 62 CHAPTER V. GRASSES CLASSIFIED ACCORDING TO THE ANATOMICAL CHARACTERS OF THE LEAF 72 CHAPTER VI. GRASSES IN FLOWER 83 CHAPTER VII. GRASSES GROUPED ACCORDING TO THEIR FLOWERS AND INFLORESCENCES 99 CHAPTER VIII. THE FRUIT AND SEED 119 CHAPTER IX. CLASSIFICATION OF GRASSES BY THE “SEEDS” (GRAINS) 135 BIBLIOGRAPHY 175 INDEX, GLOSSARY AND LIST OF SYNONYMS 177 CHAPTER I. THE VEGETATIVE ORGANS. That grasses are interesting and important plants is a fact recognised by botanists all the world over, yet it would appear that people in general can hardly have appreciated either their interest or their importance seeing how few popular works have been published concerning their structure and properties.