356 



LECTURE XV. 



2. Zone 3'5 mm. in length, at the upper end of the first internode 

 of Phaseolus multiflorus. 



Time. 



ist day (24 hours) 

 2nd 

 3rd 

 4th 

 5th 

 6th 

 7th 

 8th 

 9th 

 loth 



Increment. 

 i'2 mm. 



5'5 



14-0 



lO'O 



2'0 



The grand period of an entire internode of the flowering stem of 

 Fritillaria imperialis : the figures represent the increments in periods of 

 24 hours (Sachs). 



March 20 2'o 



21 5-2 



22 6'I 



23 6-8 



25 

 26 

 27 

 28 

 29 



I3-4 



I2'2 

 I0'6 



Inasmuch as a growing organ, a root or an internode for 

 instance, consists of a number of zones growing simulta- 

 neously, the increase in length of the organ in a given time 

 will be the sum of the increments of the growing zones, the 

 rate of its growth at a given time will be the mean of the 

 rates of growth of the zones, and its grand period will begin 

 at the commencement of that of the first zone and will extend 

 to the end of that of the last. 



The following table of observations made by Sachs upon an internode 

 of Phaseolus multiflorus illustrates the relations mentioned above. The 

 internode was marked out into 12 zones each 3*5 mm. long: the figures 

 give the daily increment in millimetres. 



It will be seen that the figures refer only to the latter part of the 

 grand period of the internode. 



