378 BOTANICAL GAZETTE [MAY 
dipped in alcohol and flamed in order to sterilize it previous to use. 
When the seeds had germinated and the roots had reached a length 
of a centimeter or more, a centimeter or thereabouts of the root tip 
was cut off in the dish with a sterile scalpel, measured, and 
transferred with a sterile platinum loop to the described culture 
medium. The growing tip of the shoot was similarly treated. 
By this method a part of the plant, including the meristematic 
region, was excised and placed under sterile controlled conditions. 
Growth of root tips in sterile nutrient solutions 
Using the method described, the root tips of peas, cotton, and 
corn were placed in (1) a modified Pfeffer’s solution,” (2) the same 
solution containing 2 per cent glucose, and (3) the modified Pfeffer’s 
solution containing 2 per cent levulose. Each root tip was trans- 
ferred to an Erlenmeyer flask of 125 cc. capacity, containing 50 cc. 
of solution. The flask was set in the dark and allowed to stand at 
room temperature during the period of the experiment. It was 
found that in such solution cultures the root tips of peas, cotton, 
and corn would develop into a considerable root system in the 
mineral nutrient solution containing carbohydrates, but that 
little growth occurred in the culture solution to which no carbo- 
hydrate was added. For all three plants the greatest growth 
occurred in the glucose solution. The method of culture and the 
appearance of root tips of corn in a 2 per cent glucose solution and 
in a solution lacking carbohydrates at the end of twenty-four days 
is shown in fig. 1. The detailed results of these early experiments 
were as follows: 
Preas.—In the experiment with peas, the variety Extra Early 
was used, and the period of growth was twenty-nine days. Fifteen 
root tips were used with each sugar solution and thirteen in the 
mineral solution without sugar. One contamination developed. 
All of the roots in the levulose solution were darkish brown, partic- 
ularly at the cut end. Those in Pfeffer’s solution were pure white. 
All were turgid, but the specific gravity of those in the Pfeffer’s 
solution was less than that of those grown in the sugar solution. 
2 The composition of this solution was as follows: 
Ca(NO,),, 2 gm.; KH;PO,, 0.5 gm.; KNO,, 0.5 gm.; KCl, 0.25 gm.; MgSO» 
0.5 gm.; FeCl;, 0.005 gm.; distilled water, 6000 cc. 
