47 



cessation of water-intake. Indeed, in most cases this 

 cessation of water-intake precedes slightly the appear- 

 ance of visible wilting in the leaves. If the injury- 

 progresses slowly, as when the outlet tubes are open 

 and the air supply is merely restricted, the cessation 

 of water-intake may precede the visible wilting by 

 several days. With heliotrope and oleander the effect 

 on water-absorption does not appear to be the same as in 

 Goleus, since the water-intake of the heliotrope decreases 

 only slowly and that of the oleander not at all. Evidently 

 these three species differ in the degree to which the 

 absorption of water by their roots depends upon the life 

 or health of the root protoplasm. Watson 2 has observed 

 the absorption of water by roots which are entirely 

 dead t and it will be recalled that the experiments of 

 Kosaroff described above indicated this same possibility 

 though the absorption was less than through living roots. 

 Kosaroff's experiments led, also, to the same conclusion 

 reached in the present work, namely, that one effect of 

 lack of oxygen in the soil is to decrease the water ab- 

 sorbing power of the roots. 



1. See pages 



2. Ann. Bot. 8: 119-120 (1894). 



