[Vol. 10 



372 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Experiment 4- — The pith of a sweet-potato, similarly suspended 

 in a jar of water, exhibited no regeneration even after 2 months. 

 Wherever regeneration occurred in any of these cultures, the 

 regenerated parts were cut out with as little of the root proper 

 as was necessary and put in killing solutions as later described 

 in preparation for histological study. Even those portions which 

 gave only a very slight indication of the possibility of regeneration 

 were used. 



SECOND SET OF EXPERIMENTS 



About 10 cc. of sand were added to each of 4 test-tubes. To 

 2 was added solution A and to the other two, solution B. These 

 were sterilized and, according to the preparation of sterile cul- 

 tures, portions, about 1 cm. square, of tobacco leaves and buds 

 were added. No regeneration occurred even after one month. 

 Similar cultures, using pieces of sweet-potato instead of tobacco, 

 were set up, but these, too, exhibited no regeneration, These 

 same experiments were repeated a few days later but with no 

 results. Either the sections were too small or the nutrient solu- 

 tions were lacking in some way or some other factor prevented 

 the regeneration which, according to Miss Kupfer, developed 

 under non-sterile conditions. A few weeks later similar experi- 

 ments were set up, using tobacco leaves and buds and pieces of 

 sweet-potato. In this case, however, a few cc. of 1 per cent cane 

 sugar and 1 per cent peptone solutions were added to the nutrient 

 solutions. No regeneration occurred, and this brought up the 

 possibility of using larger pieces. Accordingly, pieces of parsnip, 

 horseradish, and sweet-potato, about 1 cm. in thickness, were 

 placed in sterile sand cultures in ordinary quart-jars. These jars 

 were plugged with cotton and over them tumblers were inserted. 

 To these solutions were also added a few cc. of 1 per cent peptone 

 and 1 per cent cane-sugar solutions. The radish and potato 

 roots were soaked in Javelle water for 2 hours before sectioning, 

 to render the outer surfaces sterile. Within about a week all 

 pieces developed regenerated roots or shoots. The early stages 

 of these regenerated parts were removed in as small portions as 

 possible and fixed for microscopic study. 



