THE CELL. 21 



limits of vision (1 micromillitneter = yoVo "i™* — Ia'j ^^' less). 

 The longest simple grains are often 185// in length. The largest 

 compound starch-grains measure as much as 106yw in length. , 



Both starch and aleuron in the cells of Pisum sativum (Fig. 6), 

 are also of importance to the physiology of nutrition in man. 

 The seeds of LeguTumosce contain two of the most important 

 representatives of our food-materials : starch, a carbohydrate, and 

 aIeiiron,an albuminoid ; hence both non-nitrogenous and nitrogenous 

 food-substances. 



Qj) Aleuron-grains. 



Aleuron-grains or protein-grains (" Klebermehl " of Theo. 

 Hartig) form the principal albuminoid reserve materials in the 

 seeds of phanerogams, while starch-grains form the chief carbo- 

 hydrate reserve products. In order to observe the aleuron grains it 

 is advisable to fix them with a '2% alcoholic sublimate solution.' As 

 a rule they are much smaller than the accompanying starch-grains ; 

 they may, however, reach a considerable size. The aleuron-grains 

 consist of a hasal substance and chemically different inclusions. 

 The base is albuminoid ; the inclusions are either crystalloids, amor- 

 phous spherical bodies ("globoids"), or calcium oxalate crystals. 

 Of these three inclusions sometimes more than one is represented in 

 the same grain. 



{a) The crystalloids resemble the base in that they are albumin- 

 oid, but differ in being insoluble in water while the base is usually 

 soluble. They differ from true crystals in that they store coloring ma- 

 terial and are capable of imbibition and swelling. However, accord- 

 ing to ScHiMPER and Dufouk their similarit}' to crystals is perhaps 

 greater than Nageli supposed. Schimper noticed that the regular 

 crystalloids of liicimis swelled equally in all directions when placed 

 in dilute hydrochloric acid ; while in the hexagonal crystalloids of 

 Miisa Hillii the swelling was equal at right angles to the main axis. 

 In crystalloids of the Para nut the swelling parallel to the main axis 

 was either greater or less than at right angles to that axis ; hence 

 their behavior is similar to that of hexagonal crystals in response to 

 heat-expansion. The optical behavior is also analogous to that of 

 crystals : the regular crystalloids are isotropic, the hexagonal slightly 

 doubly refractive. A special peculiarity of some crystalloids is a 

 stratification noticeable in the swollen state. Fig. 8 A^ represents a 



' Pfeffer studied the aleuron-grains more particularly. 



