Chap, vi The Metabolic Processes 391 



tion on the subject of these substances had been obtained 

 prior to 1872, when Pfeffer described the development in 

 the seeds of many plants of the grains which in 1855 

 Hartig had described under the name of aleurone. These 

 grains are composed of various proteins and are usually 

 associated with some form of mineral matter. Some are 

 small and simple in structure, while others are somewhat 

 complex. Pfeffer attributed their first formation in Lupinus 

 particularly, though not exclusively, to the influence of the 

 mineral constituent associated with them. He said that the 

 latter, usually either minute crystals of oxalate of calcium 

 or amorphous collections of the double phosphate of calcium 

 and magnesium, can first be detected in the cell sap of the 

 vacuole of the cell, and slowly the protein matter accumu- 

 lates round them and encloses them in its substance. As 

 the seed ripens the sap becomes less and less watery and 

 gradually more protein is deposited by a kind of precipita- 

 tion, till the complete aleurone grain is formed. To Pfeffer 

 then, particularly in the case of the lupin, the formation 

 was almost entirely mechanical, resembling crystallization, 

 the influence of the protoplasm not appearing important. 



Pfeffer's account was not challenged till 1888, when 

 Rendle investigated the process as exhibited in the seeds 

 of Lupinus polyphyllus. The result of his researches was 

 to bring it much more closely into line with the work of 

 Schimper on the carbohydrates. Rendle observed the early 

 stages of construction beginning when the development 

 of the cotyledons was sufficiently advanced to swell out 

 the seed coat, by which time the endosperm had been 

 absorbed. At this time the peripheral layer of the proto- 

 plasm contained chlorophyll grains, in the substance of 

 which starch was accumulating. Simultaneously the aleu- 

 rone grains began to appear as, or to be preceded by, small 

 bodies of spherical or ovoid shape which projected from 

 the protoplasm. Little by little these projections increased 



