GROWTH OF ROOTS AND SHOOTS IN THE LEAF 



31 



two pieces of half stem (6 and foi) as equal in mass as possible. 

 In order to minimize the error in cutting a larger number of 

 pieces of stem were used for one experiment. One half stem b 

 (Fig. 29) was removed at once from one of each pair of sister 



Fig. 28. — Two sister leaves suspended entirely in air. The stippling indi- 

 cates the reddish pigment. In the leaf to the left, which is connected with a 

 piece of stem, the pigment flows into the axillary shoot of the stem and into 

 the petiole, and is collected in the upper part of the leaf nearest the petiole. In 

 the sister leaf, without stem, it collects near the place where the new shoots are 

 formed and in the new shoots. Duration of experiment, Feb. 17 to Apr. 5. 



leaves, and the dry weight of these half stems (b) was determined 

 immediately, the other half stem, hi, remained in connection with 

 the leaf, ai. The two sets of sister leaves (ai with a half stem 



Fig. 29. — Method of proving that the dry weight of a piece of stem kept in 

 connection with a leaf increases at the expense of the shoot and root production 

 of the leaf which is correspondingly diminished (see text). 



attached, the other a without a half stem) were suspended for 

 several weeks in moist air, their apices dipping into water (Fig. 

 30). The leaves Oi, with a half stem (6i) attached, formed a 

 smaller mass of shoots and roots than the leaves a, without such 



