THE VALIDITY OF THE MASS RELATION 



47 



plant were used for reasons to be given later. Stems with 4 

 nodes each, were split longitudinally and one half was cut trans- 

 versely into 2 pieces with 2 nodes each, a', b', and c', d', respec- 

 tively (see Fig. 39). The other half with the 4 nodes a, h, c, and 

 d was not cut. All 3 pieces were put with their base into water. 

 It was to be expected that the sum of the dry weight of the 

 shoots produced by the 2 small pieces with 2 nodes each should 



Fig. 39. — Piece of stem with 4 nodes, a, b, c, d, split longitudinally. One- 

 half cut transversely into two pieces, a', b', and c', d'. The half a, b, c, d, pro- 

 duces 1 shoot which about equals in mass the 2 shoots produced by a', b', and 

 c', d'. Duration of experiment, Dec. 9, 1921 to Jan. 4, 1922. 



equal the dry weight of the shoots produced by the larger pieces 

 with 4 nodes each. Figure 39 shows at a glance that this is 

 approximately the case and the dry weight determinations 

 confirm this. 



The first experiment was carried out on 7 stems, a second ex- 

 periment on 16 stems. Table XV gives the result. The four- 

 node pieces produced 36 milligrams dry weight of shoots per 

 gram dry weight of stem; while the two-node pieces produced 



