METHODS OF EXPERIMENTS. l7 



The seeds were put in spliagiiiuu moss finely broken up and kept 

 sufficiently moist to preclude lateral branching or superfluous devel- 

 opment of root hairs. They germinate readily in about forty-eight 

 to seventy-two hours at an ordinary room temperature. The rootlets 

 and leaves make their appearance almost at the same time. The 

 number of roots varies Avitli the variety, but is usually from three to 

 seven. Three is the average number, five is rather connnon, and 

 seven not very rare. Only one root of each seedling was marked. 

 The initial or central one was always preferred when otherwise fit 

 for the purjjose. IIoAvever, it was found after a large number of 

 tests that the central one was most likely to become deformed Avhile 

 in the sphagnum moss, the tips becoming enlarged and blunt, in which 

 case the root soon ceases to grow. When this happened side roots 

 were preferred for marking. Rootlets which are smooth and uniform 

 in thickness, with a ratlier sharp point, are most vigorous and give 

 best results. Only experience in this work can teach one which of 

 several roots is preferable for marking. The seeds Avere taken from 

 the moss, nuirked, and transferred quickly to the solution. Care was 

 taken in every way possible to avoid change of conditions during the 

 process of. making. These details will be discussed more fully in 

 another part of this paper. 



The solutions during the period of experiment were kept in the best 

 nonsoluble beakers that could be obtained, each being large enough 

 to hold about 300 c. c. After the solutions had been used once or 

 twice" the glassware was thoroughly rinsed in distilled water before 

 being used for the next test. Nearly every other day the beakers were 

 thoroughly sterilized l)y boiling in distilled water. The beaker 

 used is about ^ cm. wide at the mouth, and Avas closed by a tight- 

 fitting cork about 1 cm. in thickness. Each cork Avas perforated, 

 and into the holes Hxe small glass rods Avere inserted, bent at one 

 end, and draAvn to a sharp point. The rods Avere inserted with their 

 hooked points on the inner side of the cork, and upon each a single 

 seed Avas placed. The rods, as Avell as the corks, fit tightly and thus 

 prevent any important amount of evaporation from the solution. 

 They are free enough, hoAVCA^er, to permit of the rods being raised or 

 lowered in or out of the solution as occasion may demand. Tn no 

 case were the glass rods alloAved to come in contact Avith the solution. 



Normal solutions, made Avith Merck's best chemically pure salts, 

 Avere prepared under the supervision of Dr. F. K. Cameron, of the 

 Bureau of Soils of the Department of Agriculture, From the nor- 



o Careful titration showed no appreciable change in the concentration of the 

 solution after several seedlings had been kept in it for twenty-four hours, or 

 even when the same volume was used during a second period of twenty-four 

 hours. 



30012— No. 79—05 M 3 



