456 QUANTITATIVE LAWS IN REGENERATION. Ill 



containing also 2 nodes (4 and 5, Fig. 7), were used as controls, while 

 the middle piece (3, Fig, 7) served for the main experiment. All 

 the pieces dipped with their bases into water. 



It is obvious from Fig. 6 that the large pieces of stem (3) produced 

 larger masses of shoots than the small pieces 1 and 2 or 4 and 5 during 

 the same time and under equal conditions. It may also be pointed 

 out that these large middle pieces (3) formed their basal roots earlier 

 than the small pieces (Fig. 6), and that the mass of their roots 

 remained greater than the mass of roots in the small pieces (Fig. 7). 



It turned out that the shoot production in the most apical pieces of 

 stems 1 and 2 was usually irregular, as a rule too small, so that these 

 pieces were not well usable as controls. The basal pieces, 4 and 

 5 , however, behaved normally. It seems that this abnormal behavior 

 of the small apical pieces is found as long as the leaves connected with 

 this piece are still small and growing. It is therefore well to use in 

 these experiments that part of the stem which is naturally defoUated 

 or the leaves of which are about to fall. It may also be weU not to 

 use pieces of stem too near the roots. After 3 to 5 weeks the dry 

 weight of the shoots and of the stem used in these experiments were 

 determined. Since some of the small pieces of stem fall often a 

 victim to fungi only one of the 2 small pieces, apical or basal, was 

 used as a control. 



Experiment I. October 25, 1921, to November 25, 1921. 



Dry weight of 



shoots f>er grant 



of stem. 



6 long pieces with 6 nodes each. tm. mg. 



Dry weight of stems 9 . 260 



" " 13 shoots 0.260 28.0 



" " " roots 0.057 



Control a. 7 short basal pieces with 1 node each. 



Dry weight of stems 2 . 895 



" " " 13 shoots 0.088 30.4 



" " roots 0.003 



Control b. 12 short apical pieces with 1 node each. 



Dry weight of stems 1 . 428 



" " 18 shoots 0.0236 16.5 



It is obvious that the apical control pieces gave too small a pro- 

 duction of shoots (16.5 mg. per gram of stem), while the basal con- 



