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THE ALUMNI JOURNAL.. 



NH 4 C1, NH 4 NO s , (NH 4 ) 2 S0 4 , (NH 4 ) 3 P0 4 ; 

 the nitrates of Na, K, NH 4 , Ca and Mg 

 are readily absorbed by the plant. 



V. Potassium is required by the plant 

 in the formation of organic materials. If 

 a plant is deprived of some salt of potas- 

 sium it is found to be unable to manu- 

 facture starch. It is most abundant in 

 seeds, rhizomes and leaves, and it is sup- 

 posed to play a very important role in 

 the formation of carbohydrates and in 

 the storing of the same. Liebig ex- 

 pressed the view that it was due to pot- 

 assium salts that the carbohydrates are 

 distributed in the plant. This has not 

 been confirmed and on the other hand 

 the experiments of Nobbe indicate that 

 while the production of starch in the 

 leaves is dependent upon potassium, a 

 particular salt (KC1) is required for the 

 transportation of starch. 



VI. Calcium is especially abundant in 

 the leaves of green plants. It is found, 

 chiefly, in the cell-walls as CaC 2 4 and 

 CaC0 3 . It is also found as crystals in 

 cells and as a crust upon the surface of 

 some plants. Sachs suggests that it en- 

 ters into combination with cellulose. It 

 forms well known compounds with the 

 proteids. Calcium is absorbed by the 

 plant as nitrate, phosphate, sulphate and 

 carbonate (the last decomposes during 

 the process). The function of calcium is 

 not clear, but it is supposed to be con- 

 nected with the growth of tissues above 

 ground (as stem and leaves). It is also 

 supposed that it combines with such or- 

 ganic acids, as are not required by the 

 plant or may be even injurious to it, 

 forming insoluble harmless and waste 

 material. It is possible also that in the 

 form of crystals in conjunction with bast 

 fibres (quercus alba) it may have a 

 strengthening effect. 



VII. Magnesium occurs in aleurone 

 grains as a double phosphate of Ca and 

 Mg termed " globoid." The function of 



magnesium, like that of calcium, is not 

 understood, although it is supposed to 

 assist in the development and transporta- 

 tion of proteids. It is used in the form 

 of salts similar to those of calcium and it 

 may replace calcium in the food of 

 moulds. 



VIII. Sulphur is used by the plant in 

 the form of sulphates of NH 4 . K, Mg and 

 Ca. It occurs in plants as : (a) sulphates 

 in the cell sap ; (b) in some ^lucosides, 

 as, for instance, in myronic acid (C 10 H 9 

 O 10 NS 2 ); (c) in proteids, which contain 0.4 

 to 0.8 per cent, of sulphur ; (d) some 

 volatile oils, as that of mustard (C 3 H„ 

 CNS); (e) in some gum resins, as in asa- 

 fcetida ; (f ) and in other substances as 

 scleromucin containing 26.8 per cent, 

 sulphur In its function it is supposed 

 that the CaS0 4 as absorbed by the plant 

 is decomposed by H 2 C 2 4 , forming CaC 2 4 , 

 and the S is set free by a process of re- 

 duction and combines with the various 

 carbohydrates forming proteids, etc. Sul- 

 phur is supposed to be a necessary part 

 of the protoplasm. 



IX. Phosphorus in the form of phos- 

 phates exercises an important and bene- 

 ficial influence upon the assimilation of 

 nitrogen. It enters into the composition 

 of the organized parts of the plant in 

 nuclein and plastin (vines). Schumacher 

 holds that the alkaline phosphates ac- 

 celerate the diffusion of the difficultly dif- 

 fusible substances (albuminoids). Com- 

 bined in lecithin (C 41 H 90 NPO 9 ) it is said 

 to be contained in the actively growing 

 cells of most plants. Hoppe-Seyler and 

 Arm. Gautier, have found phosphorus in 

 the molecule of chlorophyllan (the crys- 

 talline product of chlorophyll)- 



X. Iron is a constituent that must be 

 present in the development of green 

 plants. It may be absorbed by the plant 

 in different forms. It is not clear that it 

 enters into the composition of thechloro- 

 plastid, but it is highly probable that it 



