i8o 



STORAGE OF FOOD AND WATER 



Strychnos, Coffea, Iris, Allium, Asparagus, etc., and in the cotyl- 

 edons of some Leguminosae and doubtless of some other plants. 

 As in the case of inulin, dextrose and laevulose are the materials 



from which reserve cellulose 

 is formed, and when wanted 

 for food it is transformed 

 back to sugar until only a 

 very thin primary wall re- 

 mains (Fig. 99). 



Amyloid, like reserve cellu- 

 lose, occurs as thickenings to 

 the cell-wall of endosperm 

 and cotyledons. It is colored 

 blue with a solution of iodine, 

 and in this respect is similar 

 to starch. It is found in the 

 cotyledons of Tropseolum and 

 in the seeds of Impatiens, 

 Pseonia, and some Primulaceae 

 and Leguminosae. During 

 germination amyloid is con- 

 verted into sugar and dis- 

 solved away, leaving only the 

 primary wall, as in the case 

 of reserve cellulose. 



Glucosides. — The sub- 

 stances embraced in this 

 group may be nitrogenous or 

 non-nitrogenous. They are 

 characterized by yielding sugar and some aromatic and other 

 compounds when decomposed by appropriate ferments, or when 

 boiled in dilute acids or alkalies. They are bitter to taste, 

 soluble in water, and may be isolated in crystalline form.- Some 

 of the glucosides undoubtedly serve as reserve food, but others 

 may not be of use in this way. 

 Amygdalin (CjoHj^NOjJ is a glucoside occurring in bitter 



Fig. 99. — Storage tissues of the cotyledon 

 of Impatiens Balfiamina. A, from the resting 

 seed, and B, from a germinating seed. In B 

 the amyloid thickenings of the cell-walls are 

 partly digested away. (After Frank.) 



