regarding the preparation of the solutions, the experiment loca- 

 tion and exposure, and the records of aerial conditions. 



Records are to be kept of visual observations made at the times 

 the solutions are renewed, regarding differences that may be 

 manifest among the various cultures. Attention should be given 

 to the root systems as well as to the tops of the plants. It is pos- 

 sible that a culture showing the apparently most vigorous plants 

 of a series at the end of the third week, for example, may not 

 show the most vigorous plants at the end of the fifth week, etc., 

 and these records of visual observation are planned to bring out 

 such occurrences. Without such records important features may 

 escape notice entirely. (On comparing cultures, etc., when meas- 

 urements cannot be employed, see: — Free, E. E. Plant World 

 18:249-256. 1915. 



Plant Measurements at End of Five-Week Period. At the end 

 of the seedling phase the following plant measurements are to be 

 made : — 



(1) Length of longest and shortest top in each culture, meas- 

 ured from the seed (or the position where it was attached) to the 

 extreme tip of the plant. 



(2) Fresh weight of tops for each culture as a whole. Cut off 

 each main root at its junction with the stem and consider all 

 that remains as the top of the plant. Cut tops into pieces as 

 much as is necessary, and immediately place all tops from each 

 single culture in a weighed test-tube, stoppering with rubber or 

 paraffined cork stopper. Stopper is removed when weighing 

 occurs. Weigh as soon as possible, and record fresh weight of 

 tops for each culture as a whole. Calculate this value to repre- 

 sent 5 plants in every case where the entire 5 plants are not 

 available. 



(3) Dry weight of tops for each culture as a whole. After 

 fresh weight has been obtained, dry the tops, at a lower tempera- 

 ture first and then at 102° C, and determine dry weight. It is 

 well to place tubes in a desiccator on removal from drying oven 

 and to stopper each tube as it is weighed, using the same 

 weighed rubber or paraffined cork stopper for all tubes; this 

 avoids having a large number of weighed stoppers. Of course 

 other weighing vessels, etc., may be used ; the method above sug- 

 gested seems adequate and is simple and inexpensive. 



(4) Dry weight of roots for each culture as a whole. Place 

 all root systems from single culture together and press gently 

 between sheets of blotting paper to remove most of the liquid. 



16 



