CELL-CONTENTS AND FORMS OF CELLS. 211 



hydrated chloral or sulphuric acid. The fixed oils remain 

 liquid at ordinary temperatures, whereas the fats tend to solidify, 

 and are occasionally found in the form of crystals in plant cells 

 (Fig. 116). Both of these classes are fatty acid-esters of 

 glycerin, whereas the waxes are combinations of fatty acids and 



^al 



f f 



Fig. 116. Crystals of fixed oils: A, section of seed of the oil palm (Elcris guineensis) 

 treated with an alcoholic solution of iodine and very dilute sulphuric acid, showing stone 

 cells (sc); cells with homogeneous brown content (sa); cells with yellowish granular content 

 (sa'); and cells of endosperm (en) having porous walls (x), and containing phytoglobulins 

 (crystalloids) (P, p), associated with needle aggregates of the fatty acids. B, cross section 

 of a cotyledon of cacao, heated in a solution of potassium hydroxide, showing the epidermal 

 layer (ep) with hair (d), phytoglobulin (crystalloids) (al) and aggregates of fatty acids (f). 

 C, a few cells of the cotyledons of ripe cacao seeds mounted in glycerin, showing separation 

 of sphero-crystals of fatty acids in the oil and starch-bearing cells of endosperm. — After 

 Hanausek. 



some alcohol other than glycerol (glycerin). According to this 

 distinction some waxes as myrtle wax, obtained from the berries 

 of Myrica cerifera, are classed among the fats, it being a mixed 

 glyceride of palmitic and lauric acids. 



The fatty acids which enter into the constitution of the fixed 

 oils and fats belong to more than one series of hydrocarbons. 



