I 



11 



bright, white surface. If the seeds are germinated in a proper medium 

 (sphagnum or peat moss saturated with water was actually employed) 

 the root is usually straight or nearlj^ so. These characteristics are 

 important, as they permit the easy and accurate measurement which 

 is essential to a determination of the amount of growth made during 

 a given period. The white lupine has the further advantage of being 

 a favorite subject for experiment with plant physiologists, so that 

 numerous data for comparison are available. 



In one series of experiments lupine plants were used which had 

 been grown for eleven days in a prepared culture solution, and had 

 not only developed a considerable root system, but had unfolded two 

 or three leaves in addition to the seed leaves. In these plants all the 

 processes essential to the life of a mature individual were undoubt- 

 edl}^ in full activity. As a rule, however, a much earlier stage of 

 growth was preferred, as clearly affording a more sensitive index of 

 the effect of solutions. Experiments with older plants indicated that 

 they are less delicate registers of toxic effect. An additional advan- 

 tage in using very young plants is that they are practically independ- 

 ent of the substratum so far as food suppl}^ (that is, the mineral 

 ash constituents) is concerned, that stored in the thick cotyledons 

 answering all purposes. Consequently the confusion which would 

 unavoidably arise if a culture solution of several salts containing 

 the necessary elements of plant food were introduced is avoided by 

 the employment of seedlings. 



Lupine seedlings were transferred directly from the sphagnum, in 

 which they had germinated twenty-four to forty-eight hours pre- 

 viously, to the solution in which the experiment was to be made. In 

 this stage of growth the seed leaves are still closely appressed one 

 to another, and are pale yellow in color. The initial root is 3 to 

 6 cm. long, and shows as yet no indication of the appearance of lat- 

 eral branches. Care was taken to keep the moss so wet as to preclude 

 a normal development of root hairs; and in this respect the result 

 would be the same if the radicles had been immersed in water imme- 

 diately after germination. It was desired to render as slight as possi- 

 ble the change of conditions in transferring from one medium to the 

 other. There is every reason to believe that under these circum- 

 stances the amount of injury sustained by the plants as a result of the 

 change of substratum was reduced to a minimum.^ 



' Wolf demonstrated [Landwirthsch.Versuch'-st.,6, 203. (1864)] that plants which 

 nad been grown in soil until a considerable root system was developed and then 

 shifted to an aqueous solution (as in the experiments of De Saussure and others) 

 coald not be depended upon to give as satisfactory results as plants which had 

 been cultivated from the moment of germination in aqueous solutions. But in 

 the case of seedlings transferred from loose wet sphagnum to water before any lat- 

 eral roots had appeared no difficulty of this sort need be apprehended. 



