THEORY OF REGENERATION BASED ON MASS RELATION : III. FURTHER EXPERIMENTS ON THE CAUSE OF THE POLAR CHARACTER OF REGENERATION.
1. Small stems with one large leaf in the middle produce shoots and roots chiefly at the expense of material sent into the stem by the leaf. Since the sap of the leaf can cause the formation of roots and shoots in the same notch of the leaf, it is difficult to assume that the polar character of the regeneration in the stem is due to a chemical difference in the ascending and descending sap sent by the leaf into the stem. 2. When the ascending sap sent by a leaf into the stem is caused with the aid of gravity to reach those tissues of the stem from which roots are formed, an abundant root formation is produced by the ascending sap. 3. These two observations in connection with a fact already published in a preceding paper support the idea that the polar character of regeneration in a stem of Bryophyllum is not due to any of the chemical differences between the ascending and descending sap but to a difference in the nature of the tissues or anlagen which are primarily reached by the ascending and descending sap.
Loeb
J
J
Laboratories of The Rockefeller Institute for Medical Research.