61 



in most cases brings about a heavier harvest. It is ex- 

 actly in line with the aims of the florist, who wishes cut 

 flowers that will ship well and that will stand up well in 

 heated rooms. 



A feature that is not so acceptable was the shortening 

 of the stems and contraction of the leaves in the dry air, 

 which was very marked in every trial. This is undoubt- 

 edly due, as the author has indicated, to the loss of water 

 from the foliage being so great in the dry air that the 

 roots were unable to take it up fast enough from the soil 

 to maintain the internal pressure, which necessarily pre- 

 vented the cells from duly expanding. That the differ- 

 ence in size of the organs was chiefly due to a deficiency 

 of water supply is also evidenced by the failure of the po- 

 tato tubers to properly increase and fill with starch in 

 plants grown in dry air. Of course it remains an open 

 question whether the roots would really take up sufficient 

 water, if it were supplied to them abundantly to provide 

 for the evaporation and still keep up the necessary inter- 

 nal pressure for maximum growth. This is a question 

 that can only be answered by actual experiment, which 

 so far is lacking. 



From the Bavarian investigations we may safely infer 

 that a moderately dry atmosphere promotes the substan- 

 tial development of ordinary plants, increases the strength 

 of stem and firmness of tissue, but that the full benefits 

 can only be derived when there is an adequate supply of 

 moisture for the roots. We may also believe from the 

 knowledge we have derived from other sources, that 

 plants in a dry atmosphere are less likely to take diseases. 



However, we are chiefly interested at present in the 

 plant's demand' for water. What already has been said is 



