G. E. Briggs, F. Kidd, and 0. West 



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annual plant maize has been selected since data are given by Kreusler 

 for this plant grown in four successive years. 



The first noteworthy result of this analysis is the demonstration of 

 the fact that the growth-rate varies greatly in magnitude at different 

 periods in the life-cycle of a plant such as maize in a perfectly definite 

 manner. 



Fig. 9 gives the generalised form of the growth-rate curve for maize 

 throughout its life-cycle. Although the broad form is that of a Sach's 

 grand period curve, it must be noted that it is not a grand period curve, 

 since the grand period curve as defined by Sachs is the curve of the 

 actual increment per unit of time plotted against time and not of 

 relative increment, that is, increment per unit of matter per unit of time 

 plotted against time. On the broad form of the relative growth-rate curve 



Fig. 9. Generalised form of the growth-rate curve for maize. 



for maize are superposed three secondary features, an initial fall, and 

 two subsidiary maxima on the descending limb. 



In this generalised curve the initial period A-B is the period before 

 the assimilatory organs are able to counterbalance the loss in dry- weight 

 due to respiration, and the rate of growth is consequently negative or 

 nil. The phase B-C corresponds to a phase in morphological develop- 

 ment during which the leaf-area per unit dry-weight increases to a 

 maximum. The phase C-F covers the remainder of the life-cycle of the 

 plant during which the leaf-area per unit dry-weight is continuously 

 decreasing. The subsidiary maxima D and E coincide with the time of 

 the record of the appearance of the male and female flowers respectively. 

 The minima X, Y which precede these maxima, correspond with the 

 earliest stages of flower development, and are possibly due to increased 

 respiration during that period. 



