1909.] 



Vegetable Assimilation and Respiration. 



33 



already described,* the leaves were made flaccid by exposure to sun and wind, and the 

 measurements repeated. At this stage Leaves 1 and 2 were very flaccid. Leaf 3 much 

 less flaccid but drooping. They were then immersed in water and measured after a 

 quarter of an hour, and again at the end of an hour's immersion. The measurements 

 are given in the following table : — 



Table XVIII. 



Column (I) Leaf 1, transverse. 



„ (2) „ 1, along midrib. 



„ (3) „ 2, transverse, left half -leaf. 



(-1) 2, „ right „ 



,, (5) ,, 2, along midrib. 



Columns (6), (7), (8) „ 3, as for Leaf 2. 



Numbers in centimetres. 





Leaf 1. 



Leaf 2. 



Leaf 3. 





(2.) 



(3.) 



(4.) 



(5.) 



(6.) 



(7.) 



(8.) 





14 -51 



16 -33 



9 -40 



12 -50 



9-30 



8-87 



8-76 



13 -97 



(b) When flaccid 



13 -64 



16-02 



8 -60 



11 -69 



9-19 



8-70 



8-57 



13 -91 



After immersion in water for — 



















(c) i hour 



13 -73 



16-15 



8-82 



11 -79 



9-19 



8-92 



8 -82 



14 -01 



W 1 



14 -58 



16 -38 



9 -47 



12 -48 



9 -28 



8-92 



8-87 



14 -06 



It will be observed that even Leaves 1 and 2, which had been so flaccid 

 that Sachs would probably have rejected them, more than recovered in an 

 hour's immersion. Leaf 3, which had been but moderately flaccid, recovered 

 in a quarter of an hour. It is higlily probable, therefore, that Sachs' 

 experimental half-leaves were completely recovered after the half hour's 

 immersion which he gave them. It follows that no deduction can be made 

 from his result on the ground of a shrinkage error. After all possible 

 deductions have been made it still remains substantially the same, still 

 remarkably high. 



It may be mentioned here that experiments have been carried out which 

 support Saclis' result.f The full description of these experiments, and a 

 discussion of their relation to Brown and Escombe's experiments, will be 

 postponed till more evidence has been obtained. 



Shrinkage Plimowcna in General. 



It remains to consider the phenomena of shrinkage as they appear in other 

 plants than Hclianthus annuus, and to discuss in a more general way their 

 bearing on the dry-weight method. 



* See p. 23. 



t See Thoday, D., " On Increase in Dry Weight as a Measure of Assimilation," ' Eeport 

 of the British Association, Dublin,' 190S, p. 905. 



VOL. LXXXII. — B. D 



