Factors Affecting Root Formation of Phaseolus Vulgaris.

The successful rootingof leafy cuttings inivolves three physiologieally distinct processes: initiation of root primordia; development of true roots from these initials; and mainitenance of the cutting as ani excised organ during the rooting. The first of these, where it does niot take place sponitanieously, cani be brought about in many plants by treatment with auxini. The second (outgrow^th of the roots) inivolves the formationi of cell-wall anid protoplasm; it therefore requires the supply of carbohydrates anid nitrogenous materials, together with such special substances as may be needed for root ('rowth. Normally all of these materials would be supplied fromii the leaves or froilm storage in the stem. Too little attention has been paid up to now to the third process, the maintenanice of the cutting, which, in view of the special coniditions that obtain when leaves are severed from the planit, is of great importainee. Thus, as pointed out by CHIBNALL (4), the detached leaf of many plants, ineluding Phaseolus, undergoes a rapid and extensive proteolysis. The present experimiients were, therefore, desigrned to shed some light oln the second and third of these processes. It was otur intention to study the influeniee of nutritiol, especially niitrogen niutritioni, anid other external chemical factors oni the rootiugcr and mainitenance of leafy herbaceous material. Since initernial factors must also be conisidered in such a study, attenitioni was paid to the r6le of auLxiii anid also to the separate roles of the leaves anld the stem. Materials and methods