1922] ROBBINS—ROOT TIPS AND STEM TIPS 381 
zation of the seeds, the method of handling the roots, or the culture 
solution was injurious or at least unfavorable. It is of interest 
to note that when the root curved in its growth the lateral roots 
were produced on the convex side of the root. This was found 
to be true also in the roots of all three kinds of plants, and it can 
be noted in the case of corn and pea roots in fig. 2. Jost (10) 
states that by bending the main root, development of lateral roots 
may be prevented from the concave side, and cites the lupine as 
an example after Nott. 
Corn.—Using the same methods, corn roots were investigated. 
The period of growth was eleven days in the dark, and the number 
of roots used in this preliminary experiment was three in the glucose 
solution, two in the levulose solution, and two in the mineral 
nutrient solution without sugar. The corn root tips made a much 
greater growth than the peas,-and did not show the browning so 
evident in the pea roots in the sugar solution, but were white in 
both the sugar solution and the mineral nutrient solution at the end 
of the experiment. The data in table II show that the average 
TABLE II 
Root TIPS OF CORN GROWN ELEVEN DAYS IN DARK 
Number roots Average Gain in Average 
Solution ae original length | length 11 days |number second- 
(cm.) (cm.) ary roots 
Pfeffer’s plus 2% glucose. .. § 2.3 8.33 22 
Pfeffer’s plus 2 % levulose. . 2 3.95 5.95 20 
Pfeffer’s solution. ....-.... 2 4.15 1.60 fe) 
increase in length in the Pfeffer’s solution was 1.6 cm. with no 
secondary roots, the average increase in length in the levulose was 
5-95 cm. with twenty secondary roots, and in glucose 8.33 cm. with 
twenty-two secondary roots. The appearance of the corn roots 
at the end of the experiment is shown in fig. 2. 
This preliminary experiment does not indicate, however, the 
maximum amount of growth which corn roots may make under 
the conditions described. Since the experiment was performed, sev- 
eral hundred corn roots have been grown in sterile nutrient solutions. 
Corn roots with a length of 14-17 cm. and with 80-125 secondary 
