IS 



From the experiments of others with plants cultivated in salt solu- 

 tions it would appear that Lupinus albus agrees pretty closely in 

 point of sensitiveness with other large-seeded Leguminosse, e. g. , peas 

 {Pisum sativum), beans {Phaseolus vulgaris), and, at least in some 

 cases, with the horse bean {Vicia faha) .^ 



In order to determine how closely plants of the same family corre- 

 spond in their resistance to toxic effect, and at the same time to 

 obtain data as to the behavior of a plant whose economic importance 

 in arid regions is inestimable, a number of experiments were made 

 with alfalfa (Medicago sativa). Here we have to deal with a plant 

 whose seeds are many times smaller than those of the white lupine 

 (1.5 to 3 mm. in greatest diameter). The radicle of the alfalfa seed- 

 ling is correspondingly small and delicate, and hence requires more 

 careful manipulation than does that of Lupinus. Alfalfa seeds were 

 germinated in wet blotting paper, and were transferred to the solu- 

 tions when the radicles were 1 to 2 cm. long. 



A basis for comparison of the effects of toxic solutions upon plants 

 of very different character and relationship is afforded by Heald's 

 investigations of the action of extremely dilute solutions of hydro- 

 chloric acid upon seedling peas, pumpkins, and maize. ^ This author 

 calculates that while one part of hydrogen ions (liberated by dissocia- 

 tion) in 6,400,000 parts of water killed the root tips of the pea {Pisum 

 sativum),^ one part in 3,200,000 was required to produce a similar 

 effect upon the jjumpkin {Cucurbita pepo) and one part in only 

 1,600,000 to destroy the root tips of maize [Zea mays). In other 

 words, maize offers four times and the pumpkin twice as much resist- 

 ance to the toxic effect of hydrochloric acid as do peas and lupines. 



These results emphasize the importance of extending the present 

 investigations to other plants of as widely different botanical relation- 

 ship as possible. It is also of great moment that experiments be made 

 with different stages of growth of the same plant, from the germinat- 

 ing seed to some point near maturity. It is as certain that the same 

 kind of plant at various periods of development differs in its reaction 

 to a given salt solution as that the reaction of the same plant to the 

 same solution will be affected by variations of temperature and, per- 

 haps, of illumination.^ 



1 But not always, for True [Annals of Botany, 9, 372, (1895)] found the white lupine 

 "more strongly affected by a 0.25 per cent solution than is Viciafaba by one of 

 1 per cent KNO3 content." He finds Pisum likewise more sensitive than Vicia 

 fdba. 



2Bot. Gazette, 22, 136 (1898). 



3 The white lupine appears to be about equally sensitive to H-ions, for Kahlen- 

 berg and True [Bot. Gazette, 22, 91 (1896)] determined its limit of endurance in a 

 solution of HCl to be e^V normal, while later Kahlenberg and Austin [Journ. 

 Physical Chem., 4, 557 (1900)] fixed upon ggVo normal as a more accurate limit. 



■^Storp [Landwirthsch-Versuchsst. , 13, 76 (1884)] found zinc sulphate to be 

 extremely injurious to germinating seedlings when exposed to the light, but 

 harmless, or nearly so, in the dark. 



