382 BOTANICAL GAZETTE [MAY 
roots have frequently been grown in two weeks in the dark in 
Pfeffer’s solution containing 2 per cent glucose. The maximum 
length has been that of a tip originally 2.0 cm. long. which attained 
a length of 32.5 cm. and 131 secondary roots, in forty-three days. 
Cotton.—Root tips of cotton were grown seventeen days in 
the three solutions, and with them even more striking results were 
secured than with the corn. Tips of ten roots were used in glucose, 
ten in levulose, and eleven in Pfeffer’s solution without sugar. 
The root tips in glucose lengthened very rapidly, and at the end of 
seventeen days, as indicated in table III, had attained an average 
TABLE II 
GROWTH OF ROOT TIPS OF COTTON IN STERILE NUTRIENT SOLUTIONS 
Average 
Average eye : 
soi Gain in number | Dry weight 
Solution Number of | quiginal | Jength 17 | secondary | per root 
“swig days (cm. roots per (gm.) 
Pfeffer’s plus 2% glucose... ... ie) 3.06 41.70 61 1224 
Pfeffer’s plus 2% levulose.... ’ 10 3-11 2.34 29 0.0728 
Pieffer's solution... . fu. . II 2.99 1.92 o.1 0.1240 
length of 34.8 cm., while originally they were but 3.06 cm. long. 
The cut end of the roots in glucose was very dark brown, almost 
black for 1-1.5 cm., and brownish for 3-4 cm. The root cap was 
black. In levulose the increase was much less, only 2.34 cm., and 
the whole root was dark brown. The increase in length in the 
mineral solution alone was still less, being only 1.9 cm. ‘The roots 
were pure white. The maximum growth in the glucose solution 
was that of a root tip 3.2 cm. long which attained a length of 
42.2 cm. with seventy secondary roots. In levulose the maximum 
growth was that of a root tip 2.1 cm. long which grew to 13.4 cm. 
with thirteen secondary roots. : 
Growth of root tips in agar 
The excised root tips of corn have also been grown in 1 per cent 
agar. Fig. 3 shows the growth of an excised root tip of corn at 
the end of two weeks in Pfeffer’s solution containing 1 per cent 
