MACDOUGAL— ACTION OF LIPOIDS IN GROWTH. 49 



has been a subject of study at the Desert Laboratory for many years. 

 Sections about i cm. square and having the thickness of the joint 

 10.5 mm. were placed in various solutions at 14-18° C. and their 

 changes in thickness recorded by the auxograph as below : 



Solution. Increase. Comment. 



Water 31 per cent. In 20 hours followed by shrinkage of 



2 per cent, in following 30 hours 

 KCI o.oiM 31 per cent. Continuous swelling for 50 hours 



'^ 1 15 per cent. In 12 hours followed by shrinkage of 



Saponin 0.005M \ o ^ ■ ... \. 



^ ^ i 8 per cent, in 40 hours 



Saponin .oiM 11 per cent. In 6 hours with shrinkage of 7 per 



cent, in 44 hours 



Shrinkage in the two cases treated with saponin would have 

 reduced the sections to original dimensions in a few hours more. 



It is to be noted that Boas used 2.5 per cent, solutions of saponin 

 in the treatment of the higher plants, which would be equivalent to 

 about a 0.003^ solution. 



A test was made with slices cut longitudinally from the median 

 portion of the joint consisting chiefly of large, thin-walled paren- 

 chyma. The average thickness of the trios in the swelling dishes 

 ranged from 3.5 to 4 mm. and the increase was calculated on the 

 original measurements. 



The following increases were obtained : 



Solutions. Increase. Comment. 



Water 40 per cent. Very slight shrinkage after 30 hours 



KCI 0.005M 38 per cent. Very slight shrinkage after 30 hours 



KCI 0.005M I g pgj. ^gj^,_ Decided shrinkage after 6 hours 



Saponin .005M) ^hich carried the pen back near 



the base line in 40 hours 



Cane sugar i per cent. 



Saponin o.oiAf 8 per cent. 



Saponin .005M 9 per cent. Decided shrinkage after 6 hours 



which carried the thickness back 



nearly to the original after 40 



hours 



At the conclusion of the test as above the ones hydrated in water 

 and in KCI were put in a saponin solution at 0.005M with a shrink- 

 age, most rapid in the sections first swelled in KCI, which reduced 

 them nearly to their original dimensions. 



PROG. AMER. PHIL. SOC, VOL. LXI., D, AUG. 12, I922. 



