basis for further generalizations, or, if a farmer, he may derive many suggestions, hints, and rules by which to improve his methods. Very few appreciate the extensive range of edible plants, but the lists given by E. L. Sturtevant (Agr. Sci., Vol. III., p. 174) suggest that we have in the botanical world an almost unexplored field from which to recover for the use of civilized man an endless variety of foods and fruits unknown to our present cuisine and table. Sturtevant enumerates in detail the 210 natural orders of plants recognized by botanists from the days of Linnæus to those of Bentham and Hooker. These orders include 8,349 genera and 110,663 species, and Sturtevant shows that the edible plants include only 4,233 species, representing 170 of these orders, so that only about 3 per cent of the known species of plants are now being used as food-most of them, of course, to a very slight extent, only as auxiliaries to the principal foods. The food plants extensively cultivated by man include only 1,070 species; that is to say, less than 1 per cent of all known species are cultivated anywhere throughout the known world, and those actually in ordinary use in European and American kitchen gardens represent only 211 species. The preceding numbers all refer to the phenogams, but Sturtevant gives supplementary lists covering the lower order of plants. Therefore it would seem that the present condition of agriculture and the present extent of our available vegetable foods is limited not so much by our climate and soil as by our ignorance of the laws of nature affecting plant life. We may not control the climate, but we may rear natural plants and adopt rational methods of modifying them by cultivation until they and we become quite independent of the vicissitudes of drought and frost. In conclusion I gratefully acknowledge the enthusiastic assistance that I have received from Mrs. R. S. Hotze as translator, and Mr. E. R. Miller in the preparation of the index. CONTENTS. LETTER OF TRANSMITTAL PREFACE TABLE OF CONTENTS. Influence of uniform temperature on germination of seed (De Candolle) - Influence of temperature and moisture on germination (Sturtevant). - Observations at Houghton Farm and Geneva, N. Y., by Penhallow Observations of temperature of manured soils in Japan by Georgeson - Influence of rain on temperature of the soil at Munich (K. Singer) - Soil temperatures as affected by surface slope and covering (Wollny).. Annual distribution of sunshine (Humboldt) Total quantity of heat required to ripen grain (Boussingault). The sunshine and heat required to ripen grain (Tisserand) The sunshine and heat required to form chlorophyl (Marié-Davy) Influence of absorbent media on chlorophyl (Engelmann) - Theoretical formulæ for actinometer (Arago-Davy; Marié-Davy; Fer- Intensity and duration of sunshine at Montsouris (Marié-Davy) Relative total heat received from sun and sky during any day by hori- Relative total heat received during certain months (Aymonnet) Photo-chemical intensity of sunshine (Bunsen: Roscoe). Comparison of Marchand's and Marié-Davy's results (Radau) Bellani's radiometer or vaporization actinometer (Descroix) Arago's cyanometer and Desain's thermo-electric actinometer. Recorded at United States Signal Service stations. Recorded at Winnipeg, Manitoba Total possible duration of sunshine, by decades (Schott; Libbey) PART II.-OPEN AIR WORK-EXPERIENCE IN NATURAL CLIMATES. The relation of temperature and sunshine to the development of plants- Thermometric and actinometric constants (Réaumur; Adanson; Hum- boldt; Boussingault; Gasparin; Lachmann; Tomaschek; Kabsch; Sachs; Deblanchis; Hoffmann; Herve Mangon; Belland; Marié-Davy; Wheat-General relation to climate and soil (Brewer) Cultivation of cereals-Experiments at Brookings, S. Dak.—Wheat- |