POSITION REGRESSION— MAIN STEM. 



85 



gives no adequate idea of the actual condition at the proximal end of 

 the main stem. It is altogether too high, because of the destruction of 

 the earlier whorls in most cases. At the upper end (75 to 85 whorls) we 



have only four whorls to base the 

 Mean leaf number mean on — an obviouslv insuffi- 



OO tC lD P . '' 



cient number. Leaving out of 

 account the upper and lower ends 

 of the series, we have quite as 

 good agreement between obser- 

 vation and theory as could be 

 expected. Or, we conclude that 

 the same latu of groivth describes 

 the change in mean leaf-number 

 in successively formed whorls, 

 whether the whorls are borne on 

 the main stem or on primary or 

 secondary lateral branches. 



The discussion of main-stem 

 whorls has been based on the 

 data of Series I, II, and III. The 

 other series lead to exactly the 

 same result, and consequently 

 it does not seem necessary to 

 consider them in etail in this 

 connection. 



We come finally to the consid- 

 eration of tertiary-branch whorls 

 from the standpoint of positional 

 differentiation. The same diffi- 

 culty is met here as in the case 

 of the main stem, namely, very 

 meager material. We have, how- 

 ever, sufficient data to get an idea 

 of the general conditions among 

 the whorls in this division of the 

 plant. Taking as before the 

 combined Series I, II, and III, we 

 have the observations set forth in 

 table 45. From this table I find 

 r = 0.603 ±: 0.059 

 V = 0.878 ± 0.021 

 We conclude, then, that just as in other divisions of the plant there 

 is a considerable degree of correlation between leaf-number and order 



o o 



O ui 



J 



izv: 



Fig. 16— Regression of leaf-number on position in 

 main-stem whorls, Series I, II, and III com. 

 blned. 



