Then dry in weighed test-tube, as for tops, and obtain the dry 

 weight of roots. Other suitable methods may of course be used. 



(5) Dry weight of entire plants for each culture as a whole. 

 This datum is simply the sum of the corresponding dry weights 

 of tops and roots. 



(6) Record any differences that may be manifest, but not 

 measurable in the above terms. Of course these observations 

 are to be made before plants are removed from the jar and stop- 

 per, and the whole manipulation of getting the above measure- 

 ments is to be carried out so as to prevent appreciable changes in 

 fresh weight before this is measured. Treat each culture sepa- 

 rately till its tops are in the stoppered tube, then proceed to next 

 culture. Preserve the dry material in envelopes, properly 

 marked, so that a reweighing or other future examination may 

 be made if desirable. 



3. Vegetative Phase. 



Preparation of the Plants. Germination is to be carried out 

 as for the seedling phase, and twice as many jars are to be set 

 up for the seedling phase as will be needed for the vegetative 

 phase. These cultures are to be carried through the seedling 

 phase in the manner described for that phase, but all cul- 

 tures ARE TO BE SUPPLIED WITH THE SAME SOLUTION, which 



is the one previously found to be best for the seedling phase. 

 At the end of the five-week period there should be twice as 

 many plants, all nearly alike, as are to be needed for the 

 vegetative phase. Select five or ten plants from this lot to 

 represent the average, and record for them the final measure- 

 ments of the seedling phase, as stated above. From the remain- 

 ing plants select a uniform lot for the vegetative phase. It will 

 generally not be necessary to remove plants from their corks; 

 the cork and its plants will simply continue in one of the cultures 

 of the vegetative phase. All cultures are of course left in the 

 solution used for the seedling phase until transferred to the par- 

 ticular solution to be used for that culture in the vegetative 

 phase. Plants that are not needed are to be discarded after the 

 series for the vegetative phase is entirely set up. Of course, 

 duplicate, triplicate, etc., cultures may be employed; and tripli- 

 cate control is to be included, as in the seedling phase. 



Treatment During the Vegetative Phase. All the different 

 solutions (see below) are to be tested for the vegetative phase, 

 to find out what solution is best for this phase, as will have been 

 done for the seedling phase. The procedure is the same as for 



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