94 ELEVENTH REPORT. 



Growth was measured directly Avith the metric scale, the tal)les of measure- 

 ments cannot be tabulated on account of lack of space. 



The color of the plants was very good in the case of the solutions treated 

 with the quartz. The leaves were a dark velvety green, tinged with red and 

 the plants looked natural as though grown in the open. It Avas found that 

 the plants became yellow colored and that the green color coidd be restored 

 by aeration and addition of ferric chloride solution in the proportion of one 

 cubic centimeter of .5/N ferric chloride solution to one liter of Avater. Ad- 

 (.lition of ferric chloride alone or aeration alone would not restore the green 

 color. 



There was a ciuestion as to the change in the concentration in the solutions, 

 so transpiration was allowed to continue and white crystals of minerals, 

 undetermined as yet, Avere deposited on the roots al:)OA'e the liquid, shoAving 

 concentration in some form. The specific gravity of each solution Avas tested 

 with a hydrometer and they AA^ere all found to be 1,000, shoAving change in 

 concentration so slight as not to be detected by the hydrometer. Trans- 

 piration in Knop's solution Avas just about tAvice as fast as in the other 

 solutions. This might be explained by the molecular Aveight formula of the 

 solutions as folio avs: 



25g. 

 MgCOa .5g. KCl .12g. 



Ca. Phos. .5g. 



Transpiration might be said to he iuA'ersely proportional to the concentration 

 (molecular Aveights) of the solution. 



A series of cultures Avere made each having one compound in one solution, 

 and one jar Avith only distilled Avater. Cultures in all cases Avere sterilized 

 at a temperature of 11 2o C. and a pressure of 12 pounds. Plants were put in 

 each jar and changed every day, thus exposing the roots to a different com- 

 pound each day. A sort of slime was noticed about the root tips of the ])lants 

 in solutions containing minerals but not in those solutions having just distilled 

 Avater. In the case of the jar AA'ith the ferric chloride, the dilution color 

 Avas so great as to be invisible l)y the naked eye, but the slime of the roots 

 concentrated the ferric chloride mineral so much as to give a dark brown 

 color. AVhether this slime is an indication of minerals going into the colloidal 

 condition to be absorbed and used directly by the roots is an undecided 

 question and needs a further study and in\'estigation. 



Fungi and bacteria are great sources of trouble in Avater culture experi- 

 ments, ]:)robably due to improper methods of sterilization. Cultures must 

 he Avatched as regards the amount of solution present, color of i:)lants, antl 

 foreign matters, fungi, etc. In my experiments, I had one case of an iron 

 reducing bacterium Avhich threw doAvn the ferric chloride out of solution as a 

 cinnamon red precipitate. Care should be exercised in the Aveighing out and 

 mixing of minerals. It Avas found that minerals mixed in different ways give 

 insoluble precipitates. 



Brief of a paper given before the Michigan State Academy of Science, 

 1909 and .the original manuscript Avith the Botanical Deixirtment of the 

 University of Michigan. 



UniA'ersitv of Michigan, Ann Arbor, Mich., Mav 1, 1909. 



