• 1910.] ON THE DISTRIBUTION OF PLANTS. 459 



northern coastal Xew Jersey, the results obtained are equally appli- 

 cable to the same salt marsh species as they are found distributed 

 along our eastern Atlantic coast. For stretching from the Bay of 

 Fundy along the New England, middle and southern Atlantic coasts, 

 as far south as Jupiter Inlet in Florida, are extensive salt marshes 

 covered with a vegetation which consists with minor dififerences of 

 almost the same and characteristic species. 



Possible Methods of Investigations. 



There are four possible methods open to the investigator of the 

 salt content of salt marsh soils and estuarine waters. These methods 

 have been used by chemists, soil analysts and plant physiologists. 



Method of Titration. — The determination of salt content by volu- 

 metric analysis has been the favorite one of chemists. For this 

 purpose, a tenth-normal silver nitrate volumetric solution is used, 

 prepared as follows: Dissolve 16.869 grams of silver nitrate, which 

 previous to weighing has been pulverized and dried in a covered 

 porcelain crucible in an air-bath at 130° C. (260° F.) for one hour 

 in sufficient water to measure at 25° C. {'jy° ¥.), exactly 1,000 c.c. 

 This solution is kept in dark amber-colored, glass-stoppered bottles, 

 carefully protected from dust and sunlight. A tenth-normal potas- 

 sium bichromate test solution is prepared by dissolving 4.8713 grams 

 of pure potassium bichromate, which has been pulverized and dried 

 at 120° C. (248° F.) in sufficient water to measure at 25° C. {"jy" 

 F.) exactly 1,000 c.c. To a definite volume of salt water, sufficient 

 potassium bichromate test solution is added to impart a yellow tint, 

 then the tenth-normal silver nitrate solution is slowly added from a 

 burette, stirring or agitating until the mixture acquires a permanent 

 tint, due to the formation of red silver chromate. The fluid to be 

 tested must be neutral, as free acids dissolve the silver chromate. 

 The cubic centimeters of silver nitrate solution used must now be 

 multiplied by .005850 Fresenius (.005837 Sutton, .005806 National 

 Dispensatory) to give the weight of the sodium chloride, because 

 .005850 Fresenius (.005837 Sutton, .005806 N. D.) grams of sodium 

 chloride is the equivalent of one cubic centimeter of tenth-normal 



