86 BOTANICAL GAZETTE [FEBRUARY 
grown from May 1 to August 1. The effect of lack of nitrogen 
was evidenced in four or five days by noticeable yellowing. 
Fig. 1 shows the condition of the various cultures on August 1. 
The plants with complete nutrient solution, and those without 
calcium, magnesium, or iron, grew about equally well. There was 
evidently enough of each of these elements already in the cuttings 
to care for considerable additional growth. All these plants had a 
good green color, indicating a plentiful chlorophyll supply. The 
effect of the absence of PO, or NO, was especially striking. A con- 
siderable nitrogen and phosphate supply evidently was necessary 
Fic. 1.—Coleus plants grown in various nutrient solutions: —Fe, iron lacking 
but all other essential elements present; ~—Mg, magnesium lacking, etc.; —O, all 
essential elements present; notice dwarfed condition of plants wart phosphate or 
nitrate. 
to cause any increment in the growth of the plants. The plants 
grown without PO, were very small, but the leaves were a deep 
green, even greener than any of the plants in the best soil. While 
addition of phosphorus was needed for any considerable growth 
of the plant, it was not needed for the maintenance of the chloro- 
phyll. The deep green in the phosphorus-lacking plants probably 
was due to the high nitrate supply in proportion to the size of the 
plant, for here, as in all of this work, nitrate supply or its deficiency 
seemed to determine the development or the disappearance of 
chlorophyll. The plants grown in solutions lacking one of the 
elements Ca, Mg, or Fe, and those in complete nutrient solutions 
