128 Otis F. Curtis 



make an opening thru the paraffin to the leaf scar below a bud. This 

 bud will then develop, breaking thru the un weakened paraffin layer 

 above. This may be one of several factors to be considered in the develop- 

 ment of buds at points where the subtending leaf is removed. Loeb 

 (1915) has apparently overlooked this factor of aeration in explaining 

 the development of shoots from buds on the side where a leaf has been 

 removed. He found that even the petiole of a leaf, if left, will inhibit 

 the development of the bud in its axil. It is quite possible that the petiole 

 retards aeration thru the leaf scar. 



In twigs left continuously in sugar solutions the rooting ability is 

 usually markedly reduced. This is probably due, primarily, not to the 

 sugar as such, but to the inhibitory by-products resulting from the action 

 of microorganisms on this organic matter. Most of the culture solutions 

 containing sugar for a prolonged period of time became badly contami- 

 nated and developed strong odors. In some of them alcohol could easily 

 be detected either by the odor or by the iodoform test. The twigs from 

 such cultures, when thoroly rinsed and placed in fresh water, eventually 

 developed normal roots, and in some cases (tables 15 and 16) these roots 

 were better developed than those of the check cultures. Twigs left in 

 the sugar solutions too long, however, eventually died. 



The poor results obtained in common practice when organic matter 

 is present a,re probably due to the increased production, by organisms, 

 of toxic decomposition compounds and carbon dioxide, and to the lessened 

 supply of oxygen, rather than to the direct effect on the cuttings of the 

 organic matter or of the microorganisms themselves. 



Treatment with sugars is apparently of no value when mature twigs 

 are used. Immature twigs, however, may be induced to root much better 

 by such treatment. It would appear from table 12 that solutions stronger 

 than most of those used might be more effective. Meyer (1886) 

 found that leaves of Beta vulgaris formed little or no starch when placed 

 in weak sugar solutions of about 1 per cent concentration, while stronger 

 solutions — 10 and 20 per cent — increased starch formation. 



When the air spaces of Ligustrum cuttings taken at the end of the 

 normal rest period are filled with water or with sugar or salt solutions, 

 by placing the twigs in the solutions under a suction pump a secondary 

 rest period is apparently induced. It would seem that this excess of 

 water and reduced aeration may favor the production and accumulation 



