48 



ordinary method of preparation, whereby a part of the acid is easily 

 liberated. Moreover, in boiling with water the secondary magnesium 

 phosphate is decomposed into tertiary phosphate and free phosphoric 

 acid. The inference suggests itself that this property is of great value 

 to the cells, since in the assimilation of nitrogen from nitrates, sulphur 

 from sulphates, and phosphoric acid from phosphates, the dissociation 

 of these salts would immediately x^recede assimilation; hence the easier 

 these acids are separated from the base the easier their assimilation 

 will be accomplished. However, this deduction relates more to the 

 assimilation of i:)hosphoric acid than to that of sulphur and nitrogen. 

 This latter assimilation must be possible also, to a certain degree, from 

 other sulphates and nitrates besides those of magnesia. According to 

 this view the formation of nucleo-proteids depends upon the i:)resence 

 of magnesium salts. As a matter of fact, it is found that magnesia 

 always increases where rapid development is taking place. In accord- 

 ance with this view also, very small quantities of magnesium salts can 

 be used for a great deal of work, since the same amount of base can 

 serve over and over again as the vehicle for assimilation of phosphoric 

 acid. This may also explain the fact, pointed out long ago by Adolph 

 Mayer, that "magnesia is more movable in the plant than lime is," and 

 that "magnesia, like the phosphates, follows the proteids." 



The fact that comparatively little magnesia can serve for extended 

 physiological operations may be noticed in fungi in culture solutions 

 devoid of lime, and also when seeds are left to develop in culture solu- 

 tions free from magnesia and with only a moderate amount of lime in 

 proportion to jphosphoric acid. For example, beans may reach even 1 

 meter in height in such solutions, the reserve magnesia sufficing for this 

 result. 



Besides the easy dissociation the solubility of the secondary magne- 

 sium phosphate in water must also be considered. This solubility is 

 much greater than that of the secondary calcium phosphate. When 

 100 cc. of a 0.2 per cent solution of disodium phosphate are mixed with 

 2 to 3 cc. of a 10 per cent solution of magnesium nitrate no precipitate 

 is formed, while with an equivalent amount of calcium nitrate there 

 will be a considerable precipitate. It may be inferred, therefore, that 

 the secondary magnesium phosphate is more capable of migrating in 

 plants than is the calcium phosphate, at least in neutral media and 

 in the cytoplasm and its intercellular connections. 



The alga Spirogyra is especially well adapted to show the influence 

 of magnesium salts upon the production of protein matter. This influ- 

 ence may be double, (1) in facilitating the assimilation of sulphur and 

 nitrogen from sulphates and nitrates the albumin formation as such is 

 enhanced; and (2) in making the assimilation of phosphoric acid possi- 

 ble, nucleo-proteids may be formed, so that division of the nucleus and 

 growth can proceed. If growth is as energetic as the formation of pro- 

 tein no accumulation of protein will take place, all being organized for 

 the wants of the multiplying cells. However, by reducing the amount 



