Nov. i8, 1918 Physiological Studies of Normal and Blighted Spinach 389 



6.76 per cent for the leaves and roots, respectively, of the spring collec- 

 tion, were used throughout this paper for calculating to the water-free 

 basis the results obtained with the diseased materials in question 



RELATION OF THE WATER CONTENT TO RETARDED GROWTH 



The dwarfing effect of spinach-blight was shown in the weight of the 

 plants used in a part of this work. Eighty diseased plants taken on the 

 Jones farm weighed 552 gm., with an average weight of 6.9 gm. per plant. 

 Forty-one healthy plants from the same beds weighed 647 gm., averaging 

 15.8 gm. per plant. The ratio of weights in disease and health was, there- 

 fore, I to 2.3. The leaves of the diseased plants were crisper, thicker in 

 texture, and smaller in size than those of normally grown spinach. The 

 root systems of the diseased plants were poorly developed, in comparison 

 with those of the sound plants. 



Considering the importance of water to the plant for the processes of 

 transpiration, respiration, osmotic pressure, etc., it seemed worth while 

 to make moisture estimations of the various plant tissues when in a fresh 

 condition. Especially was it desirable to find out what difference, if 

 any, there is between the healthy and the diseased spinach plants with 

 regard to their moisture content. For this purpose several spinach 

 samples were taken from various beds, immediately placed in air-tight 

 jars, and the moisture estimations made within 24 hours. The results 

 obtained are presented in Table II. 



Table II. — Moisture content of fresh healthy and diseased spinach 



HEALTHY SPINACH 



DISEASED SPINACH 



Dec. I, 1915, and Jan. 

 21, 1916. 



, do 



do 



do 



do 



May 6, 1916 



do 



do 



Entire plant . 



do 



do 



Leaves 



do 



Entire plant . 



Leaves 



Roots 



81-55 



} 83- 92 

 79.89 

 77-39 

 76.31 



