64 BOTANICAL GAZETTE [SEPTEMBER 
400 ppm of peptone and 200 ppm of autolized yeast. Both the 
yeast and peptone were sterilized intermittently at 100° C. The 
root tips were grown in the dark at room temperature. 
The beneficial effect of the peptone and the autolized yeast began 
to be evident toward the end of the second period of growth. From 
the data in table II it can be noted that the root tips in the peptone 
solution show distinctly greater growth in length, production of 
secondary roots, and greater increase in dry weight. The maximum 
increase in this period in the check was 3.2 cm. with eight secondary 
roots, in the peptone solution 3.6 cm. with twelve secondary roots, 
and in the yeast 5.5 cm. with nineteen secondary roots. The 
appearance of two of the best root tips in the Pfeffer’s solution plus 
glucose and in the same solution plus peptone at the end of the 
second period is shown in fig. 2. A number of the roots in the pep- 
tone solution, however, and still more in the autolized yeast solution 
developed very abnormally. They became swollen, translucent, 
water-soaked, and extremely brittle, and growth was stopped. 
From later experiments the large number of these abnormalities is 
believed to be due to the combined action of the peptone or yeast 
and the comparatively high room temperature of July (about 
30 ©). 
The dry weights of the root tips in the yeast and peptone solu- 
tions at the end of the second period were comparatively high, as 
can be noted from later experiments. These high dry weights were 
due to the large number of thickened and abnormal roots which 
developed in this period in the yeast and peptone solutions. Of 
the eight roots in the peptone only four were transferred, and of the 
eight roots in the yeast only two were transferred. These grew in 
the third period, however, while the check root tips did very little, 
as can be noted in table II. The maximum growth in the third 
period in the check was 0.3 cm. with no secondary roots, in peptone 
7.8 cm. with twenty-nine secondary roots, in the yeast solution 9.4 
cm. with forty secondary roots. The tips of three of the four roots 
in the peptone solution were transferred and one of the two roots in 
yeast. These grew in the fourth period, the maximum in the pep- 
tone being 4.5 cm. with no secondary roots, and in the yeast 3.5 cm. 
with four secondary roots. The one root in the yeast solution was 
