Derivations are given, but the history of the terms has not been attempted. According to the author, ‘anlage’ may be variously rendered as _rudiment_, _inception_ or _primordium_. ‘Chlorophyll’ receives the double consonant at the end of the last syllable against the popular extra-botanical practice. Regarding ‘medullary’ the author says: “I have given the accent as it is always spoken (medul’-lary) though all of the dictionaries (_botanical?_) accent it as med’-ullary except Henslow’s.” In this the author had in mind the practice among his insular colleagues only, since the latter pronunciation is given in the Standard, Century and Webster’s Dictionaries and is followed by nine tenths of the American botanists. “Mycorhizome = mycorrhiza-like structures in Corallorhiza and Epipogum roots,” and “Mycorrhiza = symbiotic fungi on the roots of plants, prothallia, etc.,” are not only incongruous with orthography and botanical fact, but also with the usage of all recent writers on this subject. While many other errors of this character could be adduced, the general value of the book is scarcely lessened, and it will be of the greatest service to the working botanist, not only in raising the general literary tone of his writings, but also in placing at his command a choice of all of the established terms dealing with any phase of the subject; an aid which will be greatly conducive to increased accuracy of statement. A decade since, the majority of the botanists engaged in the study of the distribution of plants on this continent, as well as the strict systematists, were quite unanimously of the opinion that the territory within the boundaries of the United States had been quite thoroughly explored, and that the task of the collector are well-nigh done. Despite this discouraging conclusion a few enthusiastic workers have not intermitted their labors in a more critical consideration of the floras of the newer and less thickly settled regions, with the result that scores and hundreds of new species have been brought to light each year, and the awakening interest in the subject promises a re-exploration of the great West. A striking example of the results awaiting the student in this line is afforded by Dr. Rydberg’s ‘Flora of Montana and the Yellowstone Park’ (New York Botanical Garden), which has recently appeared. Although the first collections of plants in this region were made by the Lewis and Clarke expedition nearly a century ago, Dr. Ryberg finds 163 new species and varieties in the 1,976 which he lists in this volume. Of this number 487 are found on both the eastern and western slopes of the continental divide, 268 on the eastern side only, 520 on the western side only, 42 of which are arctic and inhabit the high mountain summits, and 659 which have originated in the exact region under discussion. Seven hundred and seventy-six of the species listed were not included in Coulter’s ‘Rocky Mountain Botany,’ published a few years ago.