[ 105 ] 



No. 13. 



A NOTE ON GEOWTH AND THE TEANSPORT OF OEGANIG 

 SUBSTANCES IN BITTER CASSAVA 

 {MANIHOT UTILISSIMA). 



By T. G. MASON, M.A., B.Sc. 



[Bead Novembee 28. Printed December 28, 1922.] 



Introduction. 



A CONSIDERABLE amouut of interest has in recent years been evinced in the 

 quantitative aspects of plant grovs^th. Possibly the most significant outcome of 

 this work has been the correspondence revealed between the course of a mono- 

 molecular reaction and the rate of growth of a number of plants of a widely 

 divergent habit (cf. Reed (5)). As a result of this correspondence, Reed (6) has 

 suggested that growth is some sort of a catalytic process, and that consequently 

 the organism may be regarded as the end-product of a process in which a catalyst 

 acts upon a substrate. By otliers (West, Briggs, and Kidd (9)) the similarity to a 

 nionomolecular reaction has been referred to an increasing differentiation into 

 productive and non-productive tissues rather than to mass action. 



Some observations recently made by the present writer (3) on the growth of the 

 cotton plant seem to accord with the latter rather than the former view. It was 

 concluded as a result of this work that the correspondence with a nionomolecular 

 reaction was probably quite illusory, and that the falling-ofF in the rale of growth 

 was, on the contrary, due to a correlation factor, which found expression in a 

 deflection of the substances needed for growth from the growing-point to fruit 

 developing on the basal fruiting-branches. After the primary axis has ceased to 

 elongate it was found possible, for instance, to activate the dormant apical 

 meristem by isolating it from the growth-inhibiting influence of this factor by 

 removing it, and budding it on to a young cotton plant. The present inquiry was 

 undertaken in order to ascertain whether there was any evidence of the presence 

 of such a factor correlating the activity of the cells of the apical meristem of 

 Bitter Cassava and the expansion of its tuberous roots. 



JExperimenfal. 



Though Bitter Cassava is generally referred to as a shrubby plant, with long, 

 thick, fleshy, starch-filled, cylindrical roots, this description is scarcely applicable 

 to the plant as it grows in St. Vincent, West Indies, where the present observa- 

 tions were undertaken; for here the growing-point of the primary axis seldom 

 relinquishes its dominance over the lateral buds, which remain dormant. Con- 

 sequently the plant normally remains unbranched. 



Twenty plants were grown in a row from cuttings in the ordinary way ; the 

 cuttings consisted of pieces of the stem of twelve to eighteen internodes. Only 

 one plant was permitted to grow from each cutting. The height of the stem was 

 determined weekly over a period of eighteen weeks. The measurements, which 



SOIENT. PROC. K.D.S., VOL. XVII, NO. 13. T 



