8o 



SCIENCE PROGRESS 



total time of immersion approximates more closely to the time 

 the plants would, under natural conditions, be covered by the 

 tide. This is shown by the following figures, which relate to 

 a species of Salicornia from Erquy and represent the increase 

 calculated as the percentage of water in the succulent parts 

 at the time of immersion in 3 per cent, sodium chloride : 



Table VIII 



It has been seen that the aerial parts of the plants under 

 consideration can absorb both fresh and sea-water, and thus can 

 take advantage of any rain, dew or sea-water which may wet 

 such regions. The final question arises, Can they also utilise 

 the aqueous vapour of the atmosphere ? Experiment shows 

 that they can. Delf 1 found that a shoot of Salicornia annua, 

 the cut end of which was sealed, suspended in darkness in an 

 almost saturated atmosphere, gained 2 per cent, in weight in 

 14^ hours, after which time no visible condensation of water 

 had taken place. 



Finally, it may be mentioned that during periods of drought 

 some parts of the plant may be kept alive by the water from 

 other parts. Thus, in Suceda it was found that the old leaves 

 acted as reservoirs, yielding up their water to the more vigorous 

 ones at the tip; in Salicornia*- the contrary obtained: the 

 youngest parts were the first to show signs of lack of water 

 and the oldest last; thus in 24 hours, whilst the shrinkage in 

 length during withering of the top internode was 1 1 -9 per cent., 

 the lowest internode showed no change. 



1 Delf, Ann. Bot. 25, 485, 191 1 ; 26, 409, 1912. 



2 Loc. cit. 



