7$ SCIENCE PROGRESS 



the initial weight of the plant. The plants were then sus- 

 pended upside down in the liquid in such a manner that only 

 the succulent parts could absorb water. At the conclusion 

 of an experiment the succulent part of the plant was removed 

 and the non-succulent parts — the base of the stem, the roots, 

 etc. — weighed. Thus was obtained the weight of the succulent 

 parts before and after immersion. 



Numerous experiments showed that the plants could ab- 

 sorb water by their aerial parts. The amount thus taken up 

 varied pretty considerably ; the smallest increase, calculated 

 as a percentage of the weight of the succulent parts of the 

 plant, was 7*58 per cent., and the greatest increase 30-29 per 

 cent. When the increase was calculated as a percentage of 

 the weight of water in the succulent part, the smallest value 

 obtained was 7*24 per cent, and the greatest 35*78 per cent. 



It was also found that the amount of water absorbed was 

 greatly increased if transpiration were allowed to take place 

 after removal from the soil and before being immersed. 



The value of this accomplishment to maritime plants, 

 which often are subjected to drought, in enabling them to take 

 advantage of rain and dew, needs no comment. 



From these observations it may be expected that the 

 aerial parts of maritime plants when inundated by the tides 

 can also absorb sea-water provided that the osmotic power of 

 the cell-sap of the epidermis and subjacent tissues is greater 

 than that of the surrounding medium. Observations show 

 that although the osmotic pressure of the cell-sap of the aerial 

 parts of maritime plants may vary considerably it is, as in 

 case of the root-hairs, very high. 



For example, Halket, 1 who employed Barger's method, 

 found that the osmotic pressure of the cell-sap of the succulent 

 parts of Salicornia ramosissima, growing in a water channel, 

 was equivalent to that of a 1-15 gram molecular solution of 

 sodium chloride, which is equivalent to a pressure of 45*6 

 atmospheres at 18 C. The same species growing on higher 

 and drier ground had an osmotic pressure equal to a 1 *45 mole- 

 cular solution of sodium chloride, which is equivalent to a 

 pressure of 56*53 atmospheres. These plants are, therefore, 

 sufficiently strong osmotically to absorb sea-water, and direct 

 experiment shows that they can. 



1 Halket, New Phyt. 12, 104, 1913. 



