96 PLANT PHYSIOLOGY 



found in quantity only in the lycopods.* It is doubtful 

 whether aluminum is necessary or even useful for these 

 plants. 



The essential soil ( ash ) constituents, as shown by water- 

 culture, are salts of phosphorus; sulphur, potassium, cal- 

 cium, magnesium, and iron. Calcium seems to be un- 

 necessary for fungi, though indispensable for higher 

 plants. 



PHOSPHORUS is a constituent element of protoplasmic 

 matters. In the nucleins it may amount to 6%. According 

 to Wolff's analyses, t phosphoric oxide (P 2 5 ) constitutes 

 about one-third of the ash obtained from embryonic tissue. 

 This tissue is rich in protoplasmic matters. In older tissues 

 containing a smaller proportion of protoplasmic matters, 

 and in dead and emptied cells, the amount of phosphorus 

 compounds is much less. In the total dry weight of a 

 plant, the amount of phosphorus, calculated as phosphoric 

 acid, is slight. This is shown by the following figures J 



in lupine seeds 1.63% 



straw 0.30% 



" potato tubers 0.63% 



" wood of trees 0.05% 



Though the percentage of phosphorus in the body of an or- 

 ganism indicates the degree to which it is used, it by no 

 means indicates the degree in which it is needed. Without 

 phosphorus,- protoplasm could not exist. 



The source of phosphorus for the majority of plants is 

 the phosphates in soil and water. Other plants under 



* Pfeffer, W. Pflanzenphysiologie, I., p. 432, Engl. transl. I., p. 437. 

 L. Chamsecyparissus and //. Alpinum have 22-27% aluminum in the ash, 

 while L. phlegmfiria, Selaginella, etc., contain only traces. Yoshida, H. 

 On aluminum in the ash of flowering plants. Journ. Coll. Science, Im- 

 perial University, Tokio, 1887. In analyses of rice, wheat, oats, beans, 

 etc. the Al. varies from 0.05% to 0.27% of the ash. 



f Quoted from Versuchsstationen, Bd. 30, by Pfeffer in his Pflanzen- 

 physiologie, L, p. 407, Eng. transl. I., p. 414. 



t Frank, A. B. Lehrbuch der Botanik, Bd. I., p. 587. Also in reports 

 of State Agricultural Experiment Stations, etc., similar figures may be 

 found. 



