14 THE PLANT WORLD. 



A method which has been devised in the laboratories of the 

 Bureau of Soils of the U. S. Department of Agriculture is much 

 simpler in operation and in man}' other ways nuich more satis- 

 factory for many water culture experiments than any other with 

 which the writer is acquainted. It can be used for cultures of 

 any plant in which the stem does not increase too markedly in 

 diameter during the period of the experiment, and is well suited 

 to such plants as wheat, and the allied grasses, buckwheat, radish, 

 etc. The writer has used it mainl\- for wheat, a plant which gives 

 excellent responses to all manner of treatments and deserves a 

 more prominent place in physiological experimentation than it 

 holds at present. Seeds of wheat or some similar grain are 

 germinated on paraffin-coated disks of galvanized iron wire net- 

 ting of a convenient size, having a ^-inch mesh, and are floated 

 just at the surface of a pan of water by means of several cork 

 stoppers pinned to the under side of the disk close to its circum- 

 ference. In coating the disks they are repeatedly dipped in 

 melted paraffin and the openings are thus decreased to a size 

 allowing the needed contact with the water but keeping the seeds 

 from falling through. If, after paraffining, the openings are too 

 small, they may be enlarged by cutting out the superfluous para- 

 fin with a small cork-borer. The w^ater below the disks is from 

 two to three inches in depth. It must be changed often, several 

 times a day in warm weather, to prevent injury tc^ the seedlings 

 from the accumulation of materials which the seeds exude and 

 from the products of bacterial and fungus growth during germi- 

 nation. Fig 2 shows the method of germination. The water 

 has been removed from both pans for taking the photograph. In 

 the pan at the right the paraffined disk is supported on a ring 

 stand in order to show the corks and roots. These seedlings are 

 of the right size for placing in the bottles. 



Shortly after the first true leaf has begun to emerge from its 

 sheath the seedlings are removed from the gernnnating apparatus 

 and placed in the culture bottles. These bottles are wide- 

 mouthed and of a low, broad form, containing eight ounces,* and 



* The most satisfactory bottle wliicli has been found for the purpose is 

 No. 5677 of Elmer and Amend's catalogue of chemical supplies. It is 

 made of a green flint glass which is fairly free from the objection of 

 being soluble in water. 



