66 BOTANICAL GAZETTE [SEPTEMBER 
used instead of one. The excised primary roots of the germinated 
grains were grown eleven days in the modified Pfeffer’s solution plus 
2 per cent glucose. The tips were then cut off and transferred to 
the same solution, or to the same solution plus autolized yeast or 
peptone. Further transfers at intervals of two weeks were made, as 
indicated in table III. 
TABLE IL 
EFFECT OF PEPTONE AND gio YEAST ON CONTINUED GROWTH OF EXCISED 
co ROOT TIPS IN DARK 
: Average origi-| Average gain | Average no. | Dry weight 
Addition to Prerrer’s solu- |No. roots tips! nal length in length secondary | per 10 roots 
tion+2% glucose (cm.) (cm.) roots (gm.) 
1. December 13-December 24 
| 
INORG oe a ee 9 2.2 14.0 05 baie 
None co) oy a 13 1.9 tA.9 SF 82 is yee 
be peers een 10 1.95 12.9 98.8 ©, 1020 
PRONE Soa sacs gn vee em we 18 I $235 72 | ere 
2. December 24—January 8 
ONE) SG ee ee 9 2.1 2.46 72 0.0058 
200 ppm — yeast.. 13 4:9 4.8 at 0.0087 
200 ppm peptone........ 9 2.05 2.9 16 0.0064 
400 ppm pepto se ee oe 14 ap | 3:9 16.7 0.0097 
3. January 8—January 22 
NONE. le ee 7 1.8 0.3 ce Ea Be eriiawaaray ce 
— oben — yeast.. 10 2.06 2.9 4.36 0.0032 
oo ppm peptone........ 6 ed 0.3 2 Oe ci nig et 
sere ppm as ea PG 12 2.0 1.4 1:6 0.0035 
4. January 22-February 5 
NOME 2s ree PE OSS Bop tyne pele eees i te ae eee. So ee 
200 jen pam p yeast.. 9 ‘6 0.83 O06 hes aay 
200 ppm peptone........ 6 1 Se 9.50 Ce i aes 
400 ppm echols eeears a II ny | 0.28 Os es rere rar ary 
Again, toward the end of the second period of growth, the bene- 
ficial effect of the peptone and yeast was evident. In this case, 
however, with the lower winter temperature (ranging around 22° C. 
in the dark room used for incubation) the abnormalities so evident 
in the first experiment were not so numerous, and most of the roots 
were carried over into the third period. Here the check root tips 
again stopped growth, while those root tips in the yeast and peptone 
