The best time to gather bark is one month before the period of inflorescence, when it is rich in sap. The flowers are best gathered when about half expanded. The fruit is gathered green or ripe according to the active principle sought. The seeds should always be mature. Not all parts of the plant are equally provided with the active principle which may be localized in the root or the flower; or distinct principles may exist in different parts of the same plant. Therefore the part indicated, and only that part, should be employed. In the root the active substance usually resides in the bark, sometimes in the parenchyma that envelopes the woody tissue and rarely in the woody tissue itself, as, for example, in "rhubarb" and "pareira brava." The stem bark is also a frequent seat of the active principle, of which the outer portion contains the greater amount, according to the valuable experiments of Howard. Some plants owe their therapeutic importance to their wood, others to their leaves or flowers, and regarding the localization of the active principle in these parts we have nothing especial to indicate. The fruit, however, may have a pericarp consisting of mucilage, starch, sugar and gum, etc., while the seeds contain fatty matter, fixed or essential oils or alkaloids, as is the case with coffee and cacao. In view of these facts, we repeat that it is indispensable to use that part of each plant which I have indicated as applicable to a determined case or condition. I earnestly hope that the physicians and pharmacists practising in the Philippines may undertake investigations and experiments regarding the therapeutic properties of the plants of my native land, and that my endeavors may have acted as a stimulus or inspiration to the loyal and earnest study of the subjects that are now awakening such interest, not only in Europe and America, but in India and Japan. I should be pleased to receive notes, plants or reports of researches from any one interested in the subject matter of this book, and I shall consider it a pleasure, as well as a duty, to devote my forces, small as they may be, to aiding any one who may do me the honor to claim my assistance. T. H. P. de Tavera. Paris, April, 1892. CONTENTS. Dicotyledonous, Polypetalous.