GROWTH AND COLLOID HYDRATATION IN CACTI 
EsmMonpD R. Lone 
(WITH TWO FIGURES) 
During the growing season of 1914 (March to August), attempts 
were made to correlate growth rates of cacti in solutions of varying 
reaction and concentration with the hydratation phenomena 
exhibited on placing cut pieces of the same species in similar 
solutions. 
It was thought at first that the parallelism discovered by 
Borowrkow! in the growth rate and hydratation of Helianthus 
annuus might be expressive of a general property of plant colloids. 
This investigator found that acidity is a favoring factor in both 
the growing and the swelling rate of Helianthus, the amount of 
swelling and the amount of acceleration of growth being dependent 
upon the concentration of the acid, and differing with different 
acids, and that alkalies increase swelling and to a greater extent 
than acids, but do not appreciably affect growth. DACHNOWSK?’ 
has obtained somewhat parallel results on the effect of acid with 
beans. 
- Experiments of a similar nature were performed in this labora- 
tory upon Opuntia Blakeana, hydrochloric and malic acids (the 
latter being the acid existing in greatest concentration in the sap) 
being used as standards for the effect of acid, and sodium hydroxide 
as the standard for the effect of alkali. Growth rate and swelling 
were studied also in a nutrient solution made by diluting to 1100 cc. 
100 cc. of the following solution: calcium nitrate 6 gm., potassium 
nitrate 1.5 gm., magnesium sulphate 1.5 gm., potassium mono- 
hydrogen phosphate 1.5 gm., sodium chloride 1.5 gm., and dis- 
tilled water 600 cc. 
For the experiments on growth, joints of O. Blakeana matured 
in 1913, bearing a small flower bud or new joint, were used, the old 
' Borowrxow, G. A., Biochem. Zeitschr. 48:230-246; and so0:119-125. 1913. 
? DacHNnowskI, A., Amer. Jour. Bot. 1:412-439. 1914. 
491] [Botanical Gazette, vol. 59 
