182 VEGETABLE PHYSIOLOGY 



elements enter into very close relationship with protoplasm, 

 the former at any rate being in all probability a constituent 

 of its molecule. 



Sulphur is only taken up by the higher plants in the form 

 of sulphates of some of the metals of the other groups or 

 of ammonia. Fungi can also utilise salts of sulphurous and 

 hydrosulphurous acids when they are presented in dilute 

 solutions. 



Phosphorus is associated with the nucleus rather than 

 with the cell-protoplasm. It is contained in the substance 

 called nuclein to the extent of about 6 per cent. The 

 nuclein is apparently chiefly in the chromatin substance 

 of the nucleus. Phosphorus is also a constituent of some 

 proteins, and is probably present in the enzymes which 

 are concerned in the true digestive processes of the plant. 

 It occurs in chlorophyll also, according to Hoppe-Seyler, 

 whose analysis of this pigment has already been quoted 



(page 149). In a few plants phos- 

 phorus is temporarily stored in the 

 seeds. Examples are presented by 

 the Brazil nut (Bertholletia) and 

 the Castor-oil plant (Ricinus), whose 

 seeds contain stores of protein 



FIG. 90. CELL or RIOINUS . , . ,, , , 



SEED, CONTAINING FIVE material in the form of complex 



ALEUBONE GRAINS. grains. In the interior of these 



grains there is a small, usually 



round, substance known as a globoid, consisting chiefly of 

 a double phosphate of calcium and magnesium (fig. 90), 

 which lies side by side with a crystal-like protein body. 



Lecithin, a complex fatty body containing phosphorus, 

 is present in actively growing cells in many plants. 



Phosphorus is absorbed by the plant usually, if not 

 entirely, in the form of soluble phosphate, most frequently 

 a phosphate of calcium. Besides being important as an 

 integral part of the living substance, certain observations 

 tend to show that it assists materially in the construction 

 of proteins. 



