452 QUANTITATIVE LAWS IN REGENERATION, in 



4 short pieces of stem with 2 nodes each, having a dry weight of 

 3.214 gm., produced 8 shoots with a dry weight of 0.0668 gm.; i.e., 

 20.7 mg. of shoot per gram of stem. 



A third stem was cut into 9 pieces with 1 node each (Fig. 2) 

 possessing a dry weight of 3.270 gm., giving rise to 17 shoots with a 

 dry weight of 0.050 gm.; i.e., 15.3 mg. of shoot per gram of stem. 



The first two figures are identical, the last figure is a little low. 

 In these experiments the end of the piece may suffer (by drying out or 

 falling a prey to fungi) and this creates an error which is especially 

 noticeable when a stem is cut into many small pieces. But in spite of 

 these sources of error the results are remarkably clear and consistent. 



It seemed of interest to compare the behavior of defoliated stems 

 split longitudinally. In this case the two halves should give approxi- 

 mately equal results. 



//. Experiments with Split Stems. 



Experiments were made with stems split longitudinally as indicated 

 in Fig. 5. Only pieces from the middle of the stem of a large plant 

 were used, for reasons to be given later. Stems with 4 nodes each, 

 were split longitudinally and one half was cut transversely into 2 

 pieces with 2 nodes each, a' , h', and c', d', respectively (see Fig. 5). 

 The other half with the 4 nodes a, b, c, and d was not cut transversely. 

 All 3 pieces (Fig. 5) were put with their bases 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 equal the dry weight 

 of the shoots produced by the larger pieces with 4 nodes each. Fig. 5 

 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 experi- 

 ment on 16 stems. Table I gives the result. 



It is therefore obvious that the dry weight of the sum of the shoots 

 produced by the small pieces a', h' , and c' , d' , approximately equals 

 the dry weight of the shoots produced by the big pieces, a, h, c, and 

 d (Fig. 5), or, in other words, the mass of shoot produced at the 

 apex of the large pieces is approximately equal to the dry weight of 

 the shoots the same stems would have produced if the buds of every 

 second node had been able to grow. 



