[Vol. 2 



464 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



course of four or five days a splendid lot of vigorous, uniform 

 seedlings which have serviceably straight radicles about 2 

 inches long with no laterals yet formed is obtained by this 

 method; such seedlings are well adapted, both by their char- 

 acter and their accommodation to an aqueous medium, for 

 solution-culture work. At this stage the plumules have grown 

 to about one-half inch in length, and the plants are now ready 

 for transfer to the culture medium, an operation which is 

 easily and quickly done. This method of germination, which 

 is shown in pi. 16 fig. 2, recommends itself both by reason of 

 its simplicity and ease of operation and the certainty of secur- 

 ing excellent results. In the transfer process from the ger- 

 minating pan to the culture medium, the entire seedling was 

 always immersed and carefully rinsed in once-distilled and 

 again in twice-distilled water ; by this means the roots became 

 free of any adhering impurities. 



As containers for the cultures, ordinary glass tumblers 

 were used, the sides of which were covered with black paper 

 to prevent algal growth and the top covered with perforated 

 paraffin paper. (For a complete description and illustration 

 of the method see the paper by McCool, '13.) Ten plants 

 were grown in most cases in each tumbler ; exceptions to that 

 number will be noted in each case when the series are dis- 

 cussed in detail. Galvanized iron wire supports were used to 

 hold the plants upright when the seedlings had attained suffi- 

 cient size to require them. 



In all cases doubly distilled water was used, the second dis- 

 tillation being carried out in the laboratory with KMnC>4 

 added to the once-distilled water to oxidize any organic matter 

 that might be present. Conductivity tests of this water 

 showed it to possess a specific conductivity of 2.064x10" 

 The nutrient solution used was that of Pfeffer, redistilled 

 water being the solvent for the necessary salts. Each tumbler 

 was filled to a convenient level with either the water or the 

 full nutrient solution as the case might be, approximately 250 

 cc. being required. To replace transpiration loss, doubly dis- 

 tilled water was added as needed. 



In the early days of conductivity work on solutions, 



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