10 ANNALES DE l/LNSTITUÏ PASTEIIU 



was, thoreforo, 2.<ir)(; — 0,441 = 2,215 gm., iilmost 4 liiiK"--. 

 as much as ihal ol' lli(> 1 cm. slem. Tiic I cm. hall sloms 

 weighed fresh 1,ÎIG0 gm., the 6 cm. hall" sLcms 15,127 gni. 

 Hence the iîihibiting power oj the stems upon shoot producii an 

 in the leaf increases ivith the length and mass of the stem but 

 not as rapidly. 



Ollier experimenis gave similar results. 



The main problem bofore us was lo décide Ihe question 

 whelher or not the inhibiling eft'ect of Ihe stem upon shool 

 production in the leaf is due to Ihe absorption by the stem of 

 that material from the leaf which would hâve served for the 

 shoot production in the latter, had it been delached from the 

 stem. If this were the case it should be possible to show that 

 the stem attached to a leaf increasod in weight enough or more 

 to account for the diminution of shoot production. In order 

 to test this idea the follovving method was adopted. A pièce 

 from the stem of Bryophyllwn containing one node with its 

 two leaves, was eut out from a plant aud the stem sf)lit longitu- 

 dinally in the middle between the two leaves, ieaving one half 

 of the stem attached to each leaf. The half stem was removed 

 from one leaf and weighed direclly. The leaf whose half stem 

 was eut off and the olher leaf, with a half stem still attached to 

 it, served for the experiment. After several weeks the stem 

 was removed from the second leaf and weighed. It was inva- 

 riably found that the stem had increased in weight to an 

 amount exceeding the diminution in the production of shoots 

 in the leaf attached to it. 



While in the experiments mentioned in the first part of 

 this paper, the fresh weight s of the shoots were used for compa- 

 rison, it was found necessarv in this case to use the drv 

 weights. It was found that, while the ratio of fresh and dry 

 weight of shoots and leaves is fairly constant under the con- 

 ditions of the experiments of the first part of this paper, this is 

 no longer the case for the split stems. The percentage of dry 

 weight in a split stem is smaller immediately after the stem is 

 eut out of a plant than after it has been suspended in moist air 

 for several weeks. Since the results of the experiment dépend 

 upon a comparison of the weight of a half stem when taken 

 fresh from the plant and after some weeks, only the dry 



