214 Transactions of the Royal Canadian Institute 



Whenever wilted stems were examined, the stomata were usually and 

 for the most part closed, though as many as 5 to 10% were open. On 

 a foggy day at 9 hr. the stomata on a long thin younger internode, but 

 one well developed were for the most part open about 4 microns wide, 

 while on an old internode they were open only 2-3 microns. At other 

 times, when no wilting was evident, they were usually more or less open. 

 At 14 hr. after three hours of sunlight, they were found in every condi- 

 tion. From repeated observations of this character, I have been able 

 only to draw the rather meager conclusions that the stomata which are 

 capable of movement are certainly open in the first half of the morning, 

 that they close more or less when wilting occurs, but that they present 

 no constant aspect otherwise. That cuticular transpiration is high in 

 the growing region is an open question. 



Method of growth measurement. — A special auxanometer, suitably 

 encased, was devised for out-door registration, the lever giving a seven- 

 fold amplification. The instrument was solidly placed on the north of 

 the plant and a terminal internode occupying a north-south position 

 was selected. This position was such as to allow the insolation to fall 

 normally to the axis of the internode at all times. A special rigging 

 allowed the internode to lie in a chamber so made and adjusted that 

 the internode might lie exposed to normal conditions, or to be variously 

 enclosed. It was possible to increase the amount of light impinging on 

 the surface of the growing part by means of two mirrors, or to reduce 

 the amount and at the same time to confine it to definite regions of the 

 spectrum with blue^ and red^ screens. The humidity could be raised 

 to saturation by closing the back of the chamber, closing it above with 

 uvioF glass, and introducing moisture with an atomizer, using a tem- 

 porary lining of filter paper. The construction of the chamber allowed 

 these adjustments to be made quickly and without in the least disturbing 

 the growing part. Connection with the registering lever was made with 

 a celluloid saddle, which clasped the terminal bud without touching the 

 internodal surface, and a light chain passing round a fixed pulley. The 

 fixity of position of the base of the internode was maintained by fasten- 

 ing the top of the penultimate internode which had ceased growth to a 

 rigging just outside the chamber. Small windows allowed the entrance 

 of the top of this internode and the exit of the chain. The whole plant 

 was fixed rigidly with stakes, and the entire system so weighted and 

 adjusted that wind, rain (of which there was practica|ly none) and other 

 possible disturbing factors were excluded. The record, which was 



1 Wave lengths less than -SlOfx. 



2 Wave lengths to .6iO;u. 



' All visible spectrum to .300)U. 



