26 Mr. D, Thoday. Expe7i'mental Researches on [June 11, 



short period of little over an hour the leaves had all expanded to the extent 

 of 0*7 to 1 per cent., and in the brighter interval which followed again 

 decreased in area by nearly the same amount. 



3 67S9I0ni2I 



Ante meridianum. 



2 3 4 5 6 



PosC merididnum . 



Fi(i. 4. — Curves showing more rapid expansion of leaves of lldianthus annuus when liazt? 

 diminished the intensity of the sunlight. Bright sunshine prevailed until 11 a.m., 

 two hazy periods occurred between 11 a.m. and 3 r.M., separated by an interval of 

 briglit sunshine lasting from 12.30 to 1.30 p.m., July 24, 1908. Oidinates are the 

 percentage excess of tin? area over that at 5 a.m. on July 22. 



TlicHo ob.s(!rvalionH were followed up Ijy a scries of measurements made on 

 a single leaf (Leaf III) between 10 A.M. and 12.20 P.M. on August 1, for tlie 

 most part every 5 minutes. The curves (fig. 6) show the percentage clianges 

 in the linear dimensions, th<! coDlinuous and tb(> broken liubter lines corre- 

 K])onding rositectivoly to transverse nieasm cmcnls of the left and riglit 



