Quantitative Analysis of the Groivth o/" Helianthus annuus. 377 



phenomenon of a decrease in the respiratory index with age. Table IV 

 shows a fall in the value of the respiratory index of the stem from 0-8 on 

 the thirty-sixth day from germination to 0'08 on the 136th day from 

 germination, and, in the value of all the leaves taken together, from 1"56 

 to 0-44. 



Table VI. — Eespiration of Leaves of Helianthus annuus. 



from 

 germina- 

 tion. 



Description of leaves used. 



Number 

 of 

 leaves 

 used. 



Weight 



of 

 leaves 

 used. 



Weight 

 of an 

 indi- 

 vidual 

 leaf. 



22 

 50 



53 

 54 



59 



64 



89 



99 



112 



136 



Seedling plant (minus roots) 



Top cluster and one or two small leaves ... 

 The remaining leaves of the plant 



Top cluster of leaves: A + flower rudi- 

 ments 



B — flo wer rudiments 



2nd pair from bottom of plant (excluding 



cotyledons) 



3rd pair do 



4th pair do 



5th pair do 



Two pairs next to top cluster 



Top cluster (flower rudiments just 



appearing) 



Top cluster of leaves (including flower 



rudiments) 

 Remaining leaves of plant 



Upper {i.e. younger) leaves of the plant ,. 

 Eemaining leaves of plant 



Ail the leaves of the plant 



Leaves off the lateral branches 



Leaves off main stem 



Leaves off the lateral branches 



Upper leaves off main stem 



Lower leaves off main stem 



All the leaves of the plant 



12 



12 

 12 

 12 

 24 



grm. 

 0-630 



4-65 



16 -00 



4- 76 

 2-64 



5- 85 



11 -35 



17 -40 

 21 -90 

 23-50 

 11 -10 



3-40 



27 -80 



1-96 

 31 -70 



79 -GO 



14 -70 

 72 -50 



44-50 



77 -90 

 90-50 



78 -50 



grm. 



0-49 



0-95 

 1 -45 

 1 -83 

 0-98 



The decrease in the rate of respiration of all the leaves taken together is 

 undoubtedly an expression of the fact that the respiratory index of indi- 

 vidual leaves falls off with age— a fact previously established by Nicolas (6).* 



* Nicolas (6) showed that, broadly speaking, the rate of respiration of leaves is 

 dependent upon their age ; but this investigator did not distinguish between the changes, 

 in the rate of respiration due to differences in the age of the leaf and those due to diiTei- 

 ences of the age of the plant. 



