lOO BOTANICAL GAZETTE Ikvgvst 



fact, the entire list of chemical and physical phenomena occur- 

 ring within the cell, diverse and complicated as these are, and 

 all the factors which can influence them are involved in nutrition. 

 Disturbances in these nutritive relations may be invoked by the 

 slightest increase or decrease in any of the factors concerned. 

 The change in concentration of a single ion may result in pro- 

 found changes in the cell. And if the water form of Proser- 

 pinaca is in any way involved in the nutritive relations it must be 

 because there is some factor, however slight, acting in the water 

 that is not acting in the air. 



This we have seen cannot be connected in any way with the 

 light relations. The other possible factors are the relation to 

 temperature, to absorption of salts or ions, to carbon dioxide, or 

 to oxygen. To state, as is not uncommon, that such a phenome- 

 non is due to an increase or decrease of the general nutritive 

 condition of the plant is, of course, merely to say that it is due 

 to a change in one or more of these factors. Experiments were 

 conducted to see what effect these, as they are present in the 

 water, have on the behavior of the plant when submerged, 



3. Temperature. — Most of the experiments were conducted at 

 the ordinary temperature of the conservatory. During the win- 

 ter some were kept at temperatures so low as almost to inhibit 

 growth, this occurring very slowly. Plants also were kept near 

 the hot water pipes at a temperature so high as occasionally to 

 kill some. In the summer the highest temperatures in the sun- 

 light were used. In all of these cases duplicate experiments 

 were conducted, some in air and some in water, so that the tern- 

 perature for the two was the same. Some were entirely sub- 

 merged, some with their tips just above water, some entirely in 

 the air, and some in the air with their tips bent over into the 

 water. In all cases the form of the leaf assumed had no relation 

 to the temperature; as long as any growth occurred the growing 

 points beneath the water produced the water form. In one case 

 tvyo tips at precisely the same temperature were not a centimeter 

 apart, one beneath water and the other above, with all the rest 

 of the plant submerged, and the former produced water leaves. 



