1923] 



BEALS — REGENERATIVE PHENOMENA IN PLANTS 371 



Experimental Work 



Object. — The object of this work is to secure regeneration, to 

 find the earliest stages of the divisions of those cells giving rise 

 to the regenerated parts, and to trace the development of those 

 tissues and the relation of those regenerated parts to the tissues 

 of the original plant by means of histological study. 



Methods and materials. — The materials used were flax seedlings, 

 pieces of sweet-potato, horseradish, parsnips, tobacco stems and 

 buds, and Bryophyllum leaves. The work was carried on with 

 sterile sand cultures, water cultures, and potted cultures. Care 

 was taken to use sterile cultures that the materials might be kept 

 a longer period of time than in previous studies free from molds, 

 bacteria, etc. Sterile cultures necessitated the use of nutrient 

 solutions. The nutrient solutions used were Shive's solution (A) 

 and Duggar's solution (B). 



The following cultures were set up in test-tubes, Ehrlenmeyer 

 flasks, and quart jars, all being plugged with cotton and then 

 sterilized in the autoclave at 15 pounds pressure for 20 minutes. 

 Tumblers were inserted over the jars that no dust might sift 

 through the cotton. The test-tubes were kept in a moist chamber 

 to keep them free from dust. 



FIRST SET OF EXPERIMENTS 



Experiment 1. — Ordinary tap- water was used for the water 

 cultures. A 3-inch piece of a horseradish root was cut at the 

 top and bottom and suspended in a tumbler of water by means 

 of a wire. In about a week roots and shoots developed. Upon 

 examination they were found to have developed from the 

 cambium. 



Experiment 2. — A piece of a horseradish root was peeled so as 

 to leave nothing but the pith. This was suspended in a tumbler 

 of water which was continually refilled. After 9 days a few 

 regenerated shoots developed, but upon examination they were 

 found to have originated from a few adhering cambium cells. 



Experiment 8. — A whole sweet-potato was suspended by a 

 wire in a quart- jar of water. Within 10 days many shoots 

 developed normally from the cambium. 



