and Laboratory Methods. 



2005 



The sodium chlorid should be included to keep the solution alkaline, it 

 serves as a preservative, not as a plant food. The iron is not used as a food, 

 but is necessary for the production of chlorophyll ; if at any time the plants in 

 the cultures begin to appear etiolated, a few drops of iron chlorid solution should 

 be added to the jars. New, clean corks are now fitted to the jars, using a sharp 

 knife and a coarse file to trim them ; two holes should be cut in each cork, one 

 for the plant and one for a glass tube to admit air. The tube should project about 

 7 cm. on either side of the cork, it also provides a means for introducing fresh 

 water when necessary. The hole for the plant should be at the center of the 

 cork and about 1 cm. in diameter ; the cork is now 

 evenly divided through the center and placed in the 

 mouth of the jar. Sterilize the jars and their con- 

 tents by boiling them in a water-bath for thirty 

 minutes, or by placing them in a steam sterilizer 

 and subjecting them to hot steam for forty minutes. 

 As soon as removed from the sterilizer add distilled 

 water, if necessary, to replenish the loss from 

 evaporation during sterilization, plug the end of the 

 glass tube and the hole in the cork with cotton, 

 and allow the jars to cool. 



Seedlings of corn {Zea Mais) or of buckwheat 

 {Fagopyrum esciilentiim) are well suited for use in 

 water cultures. Select seedlings 3-6 cm. long which 

 have grown in damp sawdust ; all adhering particles 

 of sawdust must be removed by m«ans of a camel's- 

 hair brush and distilled water, finally they should be 

 rinsed with two or three changes of distilled water. 

 When the temperature of the jars is between 18° and 

 25°C. the seedlings may be placed in them. Wrap 



the seedling with a tuft of fresh, dry cotton-batting, remove half of the cork and 

 place the seedling in the semi-circular hole at the center so that the collar of 

 cotton-batting supports the seedling when the other half of the cork is replaced. 

 The cotton should never be allowed to become wet, as it is pretty sure to pro- 

 duce a growth of fungus ; on that account freshly ignited asbestos is better than 

 cotton. In the case of the corn seedling the grain should go below the cork, 

 but should not touch the liquid, the upper end of the corn or buckwheat seed- 

 ling should project above the cork. The interior of the jar must be rendered 

 dark to prevent the growth of algae in the solution ; for this purpose cover the 

 jar with an opaque jacket (Fig. 4). When finished, label the preparatioas indi- 

 cating the composition of the solution and place the cultures in a hot-house. 

 At the end of two weeks, and each week thereafter, empty the jars and refill 

 them with fresh solutions of similar chemical composition ; from time to time 

 aerate the solutions by forcing air in through the tube. Final observations may 

 be made at the end of three or four weeks. 



2. The Acidity of Roots. The presence of acid in the secretion of the root 

 may be shown by its reaction to litmus paper. Grow any seedlings with a large 



Fig. -4. — Apparatus for de- 

 termining the elements ne- 

 cessary for the nutrition of 

 plants. 



