Changes in the floristic composition are described as well as ways in which the chemical composition of the plants is altered. I was interested to learn, for example, that the application of moderate levels of nitrogen in fertilizers to a mixed sward could result in a decline in the amount of clover and conse quently an actual fall in the total nitrogen content of the sward!This book is a most useful review of the more practical aspects of nitrogen metabolism in herbage and is a most readable introduction into the subject for the plant physiologist or biochemist schooled in more esoteric metabolic cycles than the nitrogen cycle. A most lavish set of references, 516 in all, takes the tyro well into the subject. The volume of chemical investigation of plants is constantly increasing and the problem of tracking down wanted information is becoming more and more intractable. This is particularly true of alkaloid-containing plants which provide so many pharmaeologically active substances and hence attract an undue share of attention. The appearance of a supplement to the original compilation by Willaman & Schubert on alkaloidal plants to cover the decade 1957-1968, is therefore a welcome event. It consists essentially of two lists, the one recording the alkaloids obtained from individual plant species with references to original literature and the other cataloguing the alkaloids alphabetically, with an empirical formula and reference back to the plant list for the literature references. Ultimately the value of any investigation of plant products depends upon the correct identification of the material analysed. The authors very wisely point out in their introduction the importance of obtaining voucher specimens of the plants studied and housing them in an established herbarium for reference.