70 THE BOTANICAL MAGAZINE. [Vol. xxi. No. 248. 



That there exist very intimate, special relations between 

 lime and magnesia in their role as plant nutrients becomes 

 evident from the fact that magnesium salts are not poisonous 

 at all lor those lower forms of alga? and fungi which do not 

 require lime for life and propagation.^ 



In perfect accordance with this behavior is that to oxalates 

 which only are poisonous for plant life from the higher algae 

 upwards, but not for the lowest forms of algae, flagellatae and 

 fungi. The most characteristic property of oxalates being the 

 withdrawal of lime from lime compounds 2) it becomes clear 

 that lime must assume a very important position in the or- 

 ganised structure, as soon as a certain stage of differentiation 

 to higher forms is reached. 



In regard to marine algae which doubtless belong to the 

 higher algae Duggar :5) in a series of interesting investigations 

 has observed that magnesium salts exert but a very weak 

 toxic effect. But it must be taken into account that in his 

 experiments magnesium sulphate was dissolved in sea water 

 which contains already lime, further that a relatively small 

 amount of lime can depress the toxic action of a considerably 

 larger amount of magnesia and finally that the marine algae 

 contain more lime than magnesia. 4) This surplus of lime in the 

 plants can also depress the toxic effects of entering magnesia. 

 It must be borne in mind that sea water is richer in magnesia 

 than in lime (ratio = 3.8 : 1 ) and that marine algae, in order to 

 adapt themselves to this unfavorable condition, must accumu- 

 late lime in their cells, which may be done in the form of 

 organic salts. 5) 



] ) Lower forms of algfe do not require " physiologically balanced solutions" since 

 they can develop in a \% solution of magnesium sulphate in presence of more traces of 

 N, K ..<) and P 2 6 (Palmetto, Ulothrix). These forms even can develop in a h% solution 

 of manganese sulphate and can adapt themselves gradually to a A.% solution of Nacl. 



-> On the similar behavior of sodium fluorid, cf. Flora 1905, p. 336. 



■•> Trans. Acad, Be. to St. Louis, vol. XVI. No. 8. 



G-ddechens, Ann. Chem. Pharm. 1854. Also Bui. No. 1., Bureau of Plant 

 Industry, Washington L901. 



•i We avoid here the term " ion," since this may confer a wrong idea. In regard 

 to the electorolytic dissociation theory compare the important investigations of Louis 

 Kahlenberg. — 



