78 BOTANICAL GAZETTE [SEPTEMBER 
2, When excised root tips of corn are grown under sterile condi- 
tions for about two weeks in the dark in Pfeffer’s solution plus 
2 per cent glucose, and their root tips are severed and transferred to 
fresh solutions at intervals: (a) growth stops in the third period; 
(b) the addition of peptone or autolized yeast permits the root tips 
to grow for 4-6 periods; (c) a concentration of 200 ppm of gelatine, 
100 ppm of creatinine, 79 ppm of glycocoll, 50 ppm of asparagin, 
or the corn embryo extract used show no beneficial effect; (d) in 
Pfeffer’s solution lacking nitrates and containing 2 per cent glucose 
a little less total growth is made than in Pfeffer’s solution containing 
nitrates and 2 per cent glucose; (e) approximately 400 ppm of pep- 
tone is more efficient than 200 ppm; (f) autolized yeast is more 
beneficial than peptone; (g) the beneficial effect of the autolized 
yeast does not appear in the first period of growth; (/) concentra- 
tions of 10, 40, 80, 200, 400, and 800 ppm of autolized yeast (equiva- 
lent in dry matter to about one-third the concentrations given) 
show no marked difference in their beneficial effect, especially in the 
early periods; (z) the higher concentrations of yeast evidence a some- 
what greater beneficial effect in the later periods than the lower 
concentrations. 
3. When the total growth of excised corn root tips whose tips are’ 
cut off and transferred twice in a six weeks’ period is compared with 
that of root tips left undisturbed, then (a) in Pfeffer’s solution plus 
2 per cent glucose in the dark the total growth in length and produc- 
tion of secondary roots are less, the dry weight is greater; (6) in 
Pfeffer’s solution plus 2 per cent glucose and 400 ppm of autolized 
yeast there is no difference in the growth in length or secondary 
root production; the dry weight is greater. 
4. When the growth of excised root tips left undisturbed for six 
weeks in Pfeffer’s solution plus 2 per cent glucose is compared with 
the growth in the same solution to which 400 ppm of autolized yeast 
is added, there is no difference in total length. The secondary root 
production is somewhat less and dry weight somewhat greater. 
5. Excised corn root tips act as individuals. 
6. The growth of the secondary roots of an excised root is much 
greater when the primary root tip stops growth than when it con- 
tinues to grow normally. 
University or Missouri 
Cotumsta, Mo. 
