igoo-i.] Effects of Water on Foliage Leaves. 307 



During this experiment and from others used as controls in the 

 solution experiments, a few very remarkable phenomena developed. It 

 would appear as though these leaves had gone on living and performing 

 all the functions natural to them, although detached from the plant, and 

 some of them had actually increased in weight. Very many leaves 

 under such conditions develop roots from the petiole, but it was not so 

 with these. In only one case did a leaf of Primula develop roots, and 

 this one was standing in water along' with a leaf petiole of Impatiens 

 which developed an extensive root system. When the leaves were 

 gathered for the above experiment, they were immediately placed in 

 paraffin paper to render the loss by evaporation as small as possible 

 during the interval between gathering and placing in water. 



Those leaves which, during the experiments, had begun to turn 

 yellow had lost considerably in weight and showed little or no starch. 

 One leaf (not referred to in the above table) which had been gathered 

 on May 31st, remained apparently alive and fresh till October. On 

 October 15th it was becoming yellow, but showed on examination 

 considerable starch in its mid-veins. It had developed no roots. One 

 fair conclusion from these experiments is that these detached leaves 

 function* as if upon the plant, though they have no roots to supply food. 

 The petioles of these leaves were always surrounded with water for from 

 one to two inches above the surface of the liquid in the vessel, the 

 trichomes raising the water by capillar)^ action. 



The leaf of Primula stellata lends itself readily to experiments such 

 as those described in this chapter, because it will live on for months 

 without sending out roots, if the petiole be kept in water ; and the lower 

 surface being reddish, acid and alkaline reactions are clearly marked. 



These results may be summarized as follows : — 



Some solutions kill the cell by extracting water osmotically from it, 

 thus hastening its drying out. Other solutions affect the cell contents 

 without causing plasmolysis. 



Ferrous sulphate produces a blue colour which is shown on the cell 

 wall. This colour appears black when in the veins of leaves. This 

 blue colour is not produced by ferric iron, showing that it is not due to 

 the presence of tannin. 



' The rate of ascent of solution through the leaf blade varies as the 

 length of vein. 



They produce starch, retain their turgor, and keep the chloroplasts in a normal condition. 



