and methods, and takes account of all the researches that have concerned themselves directly with indicators or have employed the methods of instrument, quadrat, and succession in obtaining what are essentially indicator values. A section is devoted to a consideration of the indicator concept and a brief account is given of the special materials used in the book.

The bases and criteria of indicators are treated in detail. The former comprise physical, physiological, associational, successional, and experimental bases. The fundamental criteria are life-forms, which are regarded as comprising vegetation-forms, habitat-forms, growth-forms, and competition-forms, and the kinds of plant communities. A new and consistent classification of habitat-forms is also proposed. The kinds of indicators are considered in much detail under the four heads, factor, process, practice, and paleic indicators. The first comprises the indicators of physical factors and factor-complexes; the second are those of fire, cultivation, grazing, etc.; practice indicators have to do with agriculture, grazing, and forestry. Paleic indicators include all of these in some degree, but they warrant special treatment by virtue of their paleontologic correlations. A concise but consistent account of the climax formations of the West has been given for the first time. The various associations and formations are treated with particular reference to their indicator significance, and hence no attempt has been made to give a detailed account of them. The nature, extent, unity, and associations of each formation are first discussed, after which the associations are treated with reference to their nature, extent, consociations, sequence of dominance, societies, and clans.

A chapter each is devoted to agricultural, grazing, and forest indicators. Under agricultural indicators are considered land classification, climatic cycles, types of farming, kinds and types of crops, and cycles of production. The chapter on grazing indicators is devoted to a comprehensive account of grazing types as indicators, carrying capacity, over-grazing, range improvement, and the essentials of a grazing policy. Under forest indicators are discussed forest types, forest sites, climatic and edaphic indicators and planting indicators of afforestation and reforestation. The relation of climatic cycles to agriculture, grazing, and forestry has been considered at some length in each case.

No. 248. BRITTON, N. L., and J. N. ROSE. The Cactaceae. Descriptions and Illustrations of Plants of the Cactus Family. Quarto.

Vol. 1. vII+236 pages, 36 plates, 302 text figures. Published 1919. Price $18.00. Vol. II. In press.

Vol. III. In press.

This is a monographic treatment of the Cactus family, of which there are more than 1,000 species confined to North and South America. The work has been carried on in cooperation with the New York Botanical Gardens, the U. S. National Museum, and the U. S. Department of Agriculture. Extensive explorations have been made by the authors in the deserts of Mexico, the United States, South America, and the West Indies where the plants were studied as individuals, and observations were made on form, habit, habitat, and their relations to other species. The Cacti as treated in Volume I consist of a single order, Cactales, and of a single family, the Cactaceae; they are divided into three tribes, Pereskieae, Opuntieae, and Cereae. This volume contains the treatment of the first two tribes. The third tribe is to be treated in subsequent volumes.

The tribe Pereskieae contains the single genus, Pereskia, in which 19 species are described. The second tribe, Opuntieae, contains 7 genera, Tacinga and Grusonia, each with a single species, Pterocactus with 4, Maihuenia with 5, Nopalea with 8, Pereskiopsis with 10, and Opuntia with 264, grouped into 3 subgenera and 46 series.

The genera and species are described in detail with full synonymy. One new genus (Tacinga) and 43 new species are described. All of the genera have been illustrated and of the 312 species 267 are represented by one or more illustrations. Among the illustrations are 28 colored plates.

No. 269. JOHNSON, DUNCAN S. The Fruit of Opuntia fulgida. Octavo, 62 pages, 12 plates. Published 1918. Price $1.25.

This paper embodies a study of the occurrence and significance of certain striking peculiarities in the development and fate of the persistent self-propagating fruits of several Opuntias. The discussion is concerned primarily with the perennation and vegetative propagation of the ovary of Opuntia fulgida.

No. 140. CAMPBELL, DOUGLAS H. The Eusporangiato: The Comparative Morphology of the Ophioglossaceae and Marattiacea. Quarto, vI+229

pages, 13 plates, 192 text figures. Published 1911. Price $4.00. This memoir is a study of the comparative morphology of two orders of ferns which are sometimes known as the Eusporangiatæ. These are probably the most primitive of living ferns, and a thorough knowledge of their morphology is essential for a complete understanding of many fossil types, as well as for a clear comprehension of the relationships existing between the living ferns. The object of the investigations here presented was to make a thorough study of the developmental history of as many of the living genera as could be obtained. To this end extensive collections were made by the writer in various parts of the world, and much of the material presented is the result of investigations made upon these collections. Fairly complete material was secured of all but two of the living genera, and the investigations include a careful study of the gametophyte and embryo of all the genera investigated, as well as the structure of the adult sporophyte. No. 58. PEARL, RAYMOND. Variation and Differentiation in Ceratophyllum. Octavo, 136 pages, 2 plates, 26 text figures. Published 1907. Price $1.00. The purpose of this study was to determine, so far as possible, the biological factors concerned in the production of the particular kind of frequency curves of fluctuating variation observed for the plant Ceratophyllum. A detailed analysis or "dissection" of the gross frequency curves of variation in terms of the individual variant is made. As a result of this analysis, it is possible to give a clear and definite statement of the factors which immediately determine the degree and kind of fluctuating variation exhibited by the different parts of this plant. The effect of environmental forces on growth and differentiation, and the relationship between intra-individual, intra-racial, and inter-racial variation and correlation are considered.

For other works relating to Botany, see Nos. 24 and 30 on page 97; 81 on page 98; 112 on page 99; and 192 on page 131.

BACTERIA IN RELATION TO PLANT DISEASES.

No. 27. SMITH, ERWIN F. Bacteria in Relation to Plant Diseases.

Vol. I, quarto, XII+285 pages, 31 pls., 146 figs. Published 1905. Price $4.00.

An outline of methods of investigation of bacterial diseases of plants in the laboratory, field, and greenhouse is given, with figures and descriptions of various pieces of apparatus and of various diseases; among the latter: Pear and apple blight; brown rot of potato, tomato, and tobacco; walnut blight; wilt of cucumber and melon; leaf-stripe of broom-corn; black-spot of the plum; larkspur disease; angular leaf-spot of cotton; soft rot of cucumber; black-rot of cabbage and turnip; Stewart's disease of sweet corn; iris rhizome rot; olive tubercle. A bibliography of general bacteriology exclusive of plant diseases is included and is arranged under 57 heads; it gives brief abstracts of some of the papers, and the chronological arrangement shows at a glance the development of the subject.

Quarto,

Vol. II. History, General Considerations, Vascular Diseases. VIII+368 pages, 22 plates, 149 figures. Published 1911. Price $5.00. Volume II, although intended primarily for plant pathologists, contains much of interest to the general reader. To the student it gives, in easily understood phraseology, authentic descriptions, methods, and definitions. It is the result of personal research of the author and his assistants through a long series of years. The first 200 pages are devoted to a general discussion of the problems of plant bacteriology, such as the supposed normal occurrence of bacteria in plants; bacteria on the surface of plants; entrance of bacteria into plants; the question of parasitism; carriers of infection; specific diseases; the experimental production of parasites; manner of infection; reaction of host to parasite; a discussion of the newest ideas on plant tumors, i e., relating them to animal tumors (with some striking illustrations); tissues attacked; solvent action of bacteria; enzymes; resistance to bacterial attack; immunity; symbiosis; cross inoculations with plant and animal parasites; plants as carriers of disease; plant hygiene. Several pages are devoted to germicides and insecticides with abstracts of the more important papers published on these subjects. Chronological bibliographies are also appended. Under symbiosis there is a full account of the root-tubercles of legumes.

The last 150 pages are devoted to three vascular diseases: wilt of cucurbits, black-rot of cruciferous plants, and the yellow disease of hyacinths. On the first of these diseases little has been published and the author's observations and experiments, covering a period of 19 years, are reported in full. Each disease is discussed under the heads: Definition, host plants, geographical distribution, signs, etiology, morbid anatomy, the parasite, treatment, pecuniary losses, history, literature.

Vol. III. Vascular Diseases. Quarto, vIII+309 pages, 47 plates (4 colored), 155 text figures. Published 1914. Price $5.00.

This volume deals about equally with diseases of monocotyledons and dicotyledons, principally with diseases of sugar-cane and maize and with those of potato, tomato, and tobacco. There is a chapter on a very curious and interesting grass disease, namely that of Dactylis; also chapters on some other little-known European and tropical diseases, including those of the banana. In connection with Cobb's disease of sugar-cane, there is a discussion of the East Indian Sereh and of the South American disease known as Polvillo. A full account is given of Stewart's disease of sweet corn and all the evidence going to show that it is disseminated on the seed. The morphology and cultural characters of Bacterium solanacearum are given in full. The destructive tomato disease, due to Aplanobacter michiganense, is also illustrated and distinguished from that due to Bacterium solanacearum. Growers of tobacco will find a separate chapter on the bacterial wilts of tobacco. Original illustrations have been used, many representing all phases of the disease and the morphology and cultural characters of the parasite. As in volume II the results given depend in most cases primarily on the author's own researches, but the literature on each disease is carefully reviewed, and that difficult to obtain is abstracted in full, when it is of special interest, as in case of the copious Dutch East Indian literature on the tobacco wilt. The chronological bibliographies showing the historical development of each subject are continued.

CLIMATOLOGY, ETC.

No. 192, HUNTINGTON, ELLSWORTH, with contributions by CHARLES SCHUCHERT, A. E. DOUGLASS, and CHARLES J. KULLMER. The Climatic Factor, as illustrated in Arid America. Quarto, 341 pages, 12 plates, 2 maps, 90 figures. Published 1914. Price $5.50.

This study of changes of climate is a continuation of the work described in the author's papers in Nos. 26 and 73. It deals mainly with the relation of climate to geological, botanical, and archeological phenomena, but contains also a considerable amount of geographical description. The book begins with a discussion of the present climate of Arizona and New Mexico, and its effect upon the earth's surface and upon vegetation. Because of the aridity and scanty vegetation, deposits of alluvium are abundant and many are terraced. A consideration of whether these terraces are of climatic or tectonic origin leads to the conclusion that they are climatic, and that they indicate climatic pulsations during the period of human occupation. Numerous ruins, here and in Mexico, Yucatan, and Guatemala, point to the same conclusion and suggest the existence of at least three moist periods separated by times of aridity.

An independent investigation of the same problem, based on the method of Prof. A. E. Douglass, shows that the amount of rainfall may be determined from the thickness of rings of growth in trees. From measurements of 450 Sequoias in California a curve has been plotted showing the approximate pulsations of rainfall in California for 3,000 years. Comparison with meteorological records suggests that the pulsations consist of an alternate weakening and strengthening of atmospheric circulation, whereby climatic zones are moved first poleward, then equatorward.

This conclusion leads to an attempt to determine the cause of changes of climate, including not only recent changes, but those of geological times, which are discussed by Professor Schuchert, who lays special emphasis upon the importance of broad crustal deformation. Such deformation, however, can scarcely account for glacial and inter-glacial epochs, and much less for the pulsations indicated by the California trees. Only the solar hypothesis seems adequate. This conclusion is tested by investigating the possibility of a connection between variations in sun spots and changes in the growth of trees. Such a connection seems to exist, and various phenomena suggest that apparent discrepancies are in reality results that would naturally be expected.

Chapters 2, 4, 5, 6, and 10 deal with the geological problem of the effect of aridity upon surface forms and upon subaerial deposits. The problem of the tectonic versus climatic origin of alluvial terraces in dry mountain regions is treated at length. Chapters 19, 20, and 21 discuss theories of climatic changes, special emphasis being given to the solar hypothesis as the cause of changes of the magnitude of glacial epochs or less, and to crustal deformation as the cause of greater changes, such as glacial periods.

Inasmuch as botanical evidence is largely used in elucidating the climate of the past, Chapter 2 describes the arboreal desert of the southwestern United States. Chapters 11 to 14 discuss the relation of the thickness of rings of growth to climatic conditions, not merely in the case of the Sequoia of California, but among trees from all parts of the country. The evidence presented in Chapters 15, 16, and 17 suggests that in equatorial regions plant formations may be displaced by climatic changes with a degree of rapidity which must cause the process of natural selection to act with greater speed than is commonly supposed.

The climate of the past stands in vital relation not only to geology and botany, but to men. Hence it is necessary to consider fully the ruins of the Southwest and the conditions under which the people lived. This is done in Chapters 6 to 10. The ruins and civilization of the Mayas in Yucatan and Guatemala are also important lines of evidence, and in Chapters 15 to 18 the theory is advanced that when the Mayas were in their prime the lowlands of this region were decidedly drier than now.

No. 289. DOUGLASS, A. E. Climatic Cycles and Tree-growth. A Study of the Annual Rings of Trees in Relation to Climatic and Solar Activity. Octavo, 127 pages, 11 plates, 40 figures. In press.

This volume describes a study of the correlation between the annual rings of trees and rainfall and solar activity. The rings of the yellow pine, Pinus ponderosa, in the dry climate of northern Arizona, are found to vary approximately with local rainfall. Ring records by this tree are carried back over 500 years. The growth of the Scotch pine, Pinus silvestris, near the Baltic Sea, varies in cycles closely corresponding to the sunspot cycle. The great sequoia, Sequoia gigantea, whose ring record is carried back over 3,200 years, shows persistent 11-year and other short-period cycles. The periodograph, an instrument specially designed for detecting and studying short cycles, is described.