22 COMPENDIUM OF GENERAL BOTANY. 



cell suspended in oil ; the crystalloids are not visible because they 

 have the same refractive index as the oil. 



(ft) Globoids may be studied by first dissolving the aleuron and 

 eventually also the crystalloids by means of dilute potassium-hydrate 

 solution. The globoids are not soluble. According to Pfeffer they 

 consist of a double phosphate of lime and magnesia. The smallest 

 approach the limits of vision ; the largest are about 10/* in dia- 

 meter. They are amorphous and isotropic, and hence produce no 

 polarizing light effects. 



(y) Crystals of calcium oxalate are usually found in such 

 aleuron-grains as contain no other inclusions. They are insoluble in 



A fi 



FIG. 8. Endosperm-cells of Ricinus communis. 



A. as seen suspended in oil; B, in potassium iodide-iodine solution, g, globoid; fc, crystal- 

 loid. (After Frank.) 



dilute acetic acid. They usually occur in star-shaped clusters 

 (Krystalldrusen). 



The several inclusions are already formed before the develop- 

 ment of all the aleuron-grains, and are subsequently surrounded by 

 a deposit of aleuron. 



Protein crystalloids (a) not only occur in aleuron-grains, but 

 they are sometimes also found in the nucleus, frequently within 

 chromatophores (associated with an oily substance), and sometimes 

 in the cytoplasm or the cell-sap. 



(c) The Remaining solid dead Inclusions of the Cell. 



Fat-crystals seldom occur, although fats are plentifully distrib- 

 uted in the cell. This is because the plant-fats are liquefied at 

 ordinary temperatures and are therefore classed with the fatty oils 

 (page 24). Solid coloring substances are found here and there 



