IV.—The Effect of Malnutrition on Root Structure

Abstract

Summary1. Reference is made to experiments conducted by Flaskämper as a result of which he stated that the removal of the cotyledons at an early stage from seedlings of Phaseolus sp. and of Vicia Faba resulted in an elimination of the pith from the subsequently formed part of the root in both species, and further induced a reduction in the number of poles in the root of the second species.2. The significance of such observations in a consideration of the theory of the Size Factor is pointed out.3. The experiments have been repeated. The malnutrition resulting from the decotylation affected the varieties employed in the present work more adversely than with Flaskämper, and usually caused the death of the seedling after a shorter or longer period.4. Sufficient evidence has been obtained, however, to throw very serious doubt on Flaskämper's conclusions. The two reduction phenomena he described are now shown to occur in the normal development of the roots of these species, and there is no indication that their occurrence is affected by decotylation.5. A teleological explanation, based on the theory of the Size Factor recently advanced by Bower, is made of this reduction in the number of protoxylem poles which occurs in the normal development of the roots of these plants.6. The significance of the appearance of a pith in the basal parts only of these roots is discussed.In conclusion, I desire to express my indebtedness to Professor F. O. Bower, F.R.S., for his constant interest in this work, and to thank Dr S. Williams and other members of the Botany Department for much valuable help. Also my best thanks are due to the Executive Committee of the Carnegie Trust for a grant towards the expense of the illustrations both of the present work and those of a recent paper on “The Stem-Endodermis in the Genus Piper,” published in the Transactions of the Royal Society of Edinburgh.