THE STORAGE OF RESERVE MATERIALS 251 



oil plant in which some of them are lying. The figure 

 represents the cell after treatment with alcohol, and subse- 

 quently with water. The alcohol removes the oil with 

 which the cells are filled, and which obscures the appear- 

 ance of the grains. The latter are of ovoid shape, and as 

 they lie their structure is not apparent, Water dissolves 

 part of the outer portion, leaving visible the ovoid body, 

 which becomes transparent. Embedded in it are a large 

 regular crystal of proteid matter, and a small rounded 

 irregular mass of minute crystals of mineral matter. These 

 two constituents are spoken of as the crystalloid and the 

 globoid respectively. The part of the matrix which is not 

 soluble in water will dissolve in a 10 per cent, solution of 

 common salt, while the crystalloid is soluble only in a 

 saturated solution. The globoid is a double phosphate of 

 magnesium and calcium. 



Examination of these grains and their reactions shows 

 that several proteids can be detected in them. Those 

 soluble in water are albumoses, while the others which 

 dissolve only in salt solutions are globulins. In grains 

 met with in other plants, proteids occur which are albu- 

 minates and dissolve only in dilute alkalis. 



Crystals of proteid occur in other places than seeds. 

 If we examine a young potato, we find, in certain cells 

 lying a little below the epidermis, some regular transparent 

 cubical crystals, which are composed apparently of the 

 same material as the crystalloids of the complex aleurone 

 grains described. They are soluble in saturated solutions 

 of common salt. Similar crystals are met with in the 

 tissues of certain seaweeds. Many of them can be made 

 to crystallise from the solvents which are used to extract 

 them. 



The seeds of the cereal grasses contain two other very 

 curious reserve proteids, which give rise in the flour to a 

 peculiar sticky material which is generally known as 

 gluten. They do not appear to be present in the aleurone 

 grains of the seeds, but to occur in the starch-containing 



