948 



SCIENCE. 



[N. S. Vol. XXI. No. 547. 



present in each pot. No explanation is 

 offered of this remarkable diversity of ac- 

 tion, but within the past few months an- 

 other paper has appeared which may 

 throw light upon the results given. True 

 has ascertained that finely divided paraffin, 

 quartz sand, filter paper or other insoluble 

 substances are all found to reduce the toxic 

 action of the deleterious salt. It is ex- 

 plained on the assumption of an absorption 

 of the toxic molecules by the surface of the 

 insoluble particles. Increasing the num- 

 ber of grains of sand, for instance, in any 

 toxic solution produced the same effect as 

 increasing the dilution. From the results 

 of these two papers it would seem, there- 

 fore, that we have two entirely different 

 sets of conditions to deal with when any 

 test of such action is made in water cul- 

 tures, on the one hand, and in soils, on the 

 other. If Kanda's results are confirmed, 

 an extensive series of tests with both fungi 

 and higher plants should be made in order 

 to determine some relation which may give 

 a working basis for further comparisons. 

 In fact, much of the work thus far done 

 will have to be reexamined in the light of 

 these results, for if any precipitate or 

 other solid particles have been present in 

 the solutions, an error will enter into the 

 calculations. The question will also arise 

 if the surface extent of the vessel used in 

 the culture is of any consequence. The 

 practical bearing of these results in the 

 treatment of soils is a matter which may 

 prove of unusual economic interest. 



Loew observed that marked injury re- 

 sults when such a plant as Spirogyra is 

 placed in a solution of a magnesium salt, 

 or in a solution in which magnesium is in 

 excess. From all of the results obtained 

 Loew has inferred that there is present in 

 all plants requiring calcium an essential 

 ealcivim protein compound. When mag- 

 nesium must, owing to the predominance 



of this element, be substituted for calcium 

 in this proteid compound there results a 

 lessening of the capacity for imbibition, 

 attended by unfavorable consequences. It 

 has been further ascertained by the work 

 of May, Kearney and Cameron, Kusano, 

 Aso and others, that there is for each plant 

 a certain more or less definite relation be- 

 tween calcium and magnesium. Neverthe- 

 less, further experimental proof is needed 

 before this brilliant hypothesis may be ac- 

 ceptable in its entirety. It may here be 

 noted that in a paper read by the writer 

 before the Society for Plant ]\Iorphology 

 and Physiology it is indicated that mag- 

 nesium compounds exert upon the marine 

 algiTe the least injurious action of all 

 nutrient bases. On the other hand, it has 

 not been demonstrated that the marine 

 algJK require calcium. 



The general phenomenon of chemotaxy, 

 or chemotropism, demands searching in- 

 vestigation in view of the recent work of 

 Jennings on flagellates, that of Newcombe 

 on root responses, and other studies on the 

 fungi. There is much to be done in de- 

 termining the effects of heat and cold 

 upon special processes, in a study of the 

 relations of temperatures to other condi- 

 tions of the environment, and in sho-\ving 

 the limitations of accommodation phe- 

 nomena. In the latter study, moreover, 

 the effects' of accommodation upon the 

 general constitution of the organism should 

 be followed. Stimulation at high or low 

 temperatiires merely expresses an intensi- 

 fied or modified irritability. It may be 

 observed in this place that death at the 

 supramaximal or subminimal may be due 

 to changes of a very definite nature: but 

 as Vines has indicated, this means very 

 little. To say that death at the supra- 

 maximal is due to the coagulation of an 

 albuminoid as suggested by Kuehne is in- 

 sufficient. For the immediate effect upon 



