MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 337 



Carmel. Tucson. 



Water 9I-I5 80.34 



Total sugars 2.61 4.30 



Total polysaccharides 1.94 3. .so 



Hexose polysaccharides 09 1.65 



Disaccharides 07 0.04 



Hexoses 52 0.06 



Pentoses 14 0.05 



Pentosan i .70 i .74 



Under natural condition similar relations exist. The following 

 table gives typical results of a large number of analyses of Opuntia 

 sp. made during each month : 



Date. 



March April 

 7- 3- 



Dry weight 1 15.25 18.20 



Total sugars I 3.49! 4. 11 



Polysaccharides [ 2.80J 3.13 



Monosaccharides. . . . : 0.691 0.98 



April 



18.90 

 5.58 

 4.70 

 0.88 



May 



5- 



21.30 

 4.81 

 4-55 

 0.26 



June 

 9- 



26.74 

 6.52 

 6.31 

 0.21 



July July 

 3. 31- 



30.32 16.45 

 5.07 2.42 

 4.92 2.26 

 0.15' 0.16 



Sept. 



19.66 



4-30 

 4.24 



O.II 



Oct. 

 26. 



20.3 



4.24 

 4.06 

 0.18 



Nov. 

 15- 



23.05 

 4.80 

 4.40 



Dec. 



30.1 

 5-70 



5.2s 



0.40I 0.4s 



Naturally conditions are somewhat more complicated than those 

 in the tests described on p. 336. At the time the new shoots begin 

 to grow, during the end of March and early April, after the winter 

 rains, the parent joints have a high monosaccharide content. As the 

 dry summer advances the amount of these sugars diminishes, 

 although the total sugars increase. With the advent of the summer 

 rains, at the end of July, the decrease in monosaccharides is checked 

 though the high temperatures and resulting high rate of respiration 

 does not permit an accumulation. Another factor entering here is 

 the effect of the temperature on the enzymatic equilibrium. Sepa- 

 rate experiments have shown that at the temperatures which prevail 

 in the cacti at this time (during the day as high as 55° C.) there is 

 a distinct shifting in favor of the polysaccharides. During the dry 

 months of September and October the monosaccharides drop to a 

 minimum, in spite of the temperature being considerably lower. 

 With the winter rains there is again an accumulation which is main- 

 tained during the winter until spring, when the favorable tempera- 

 tures again permit growth. The formation of new shoots does not 

 take place in spring when an accumulation of monosaccharides has 



PROC. .\MER. PHIL. SOC, VOL. LVI, W, JULY 30, I917. 



