42 



FUNDAMENTALS OF CYTOLOGY 



with it are other materials; these will be discussed in Chap. VI. Cellulose 

 and hemicelluloses frequently serve as reserve products, notably in the 

 endosperm of certain seeds. 



Fig. 31. — Cell from stem of an angio- 

 sperm {Pellionia) with large starch gran- 

 ules. Most of the plastid substance forms 

 a thick cap at one end of the granule. 



Fig. 32. — Potato-starch granules photo- 

 graphed through a polarizing microscope 

 with crossed Nicol prisms. 



Glycogen is an important reserve carbohydrate formed in animal 

 cells; it occurs also in blue-green algae and various fungi. Mucilages 

 and gums are further examples of ergastic carbohydrates. 



Fig. 33. — Large oil drop- 

 let in cell of young root of 

 heliotrope ( Valeriana) . 

 {After A. Meyer.) 



Fig. 34. — Development of crystal aggregate ("druse") 

 in castor bean plant. 1-5, single crystals and aggregates; 

 6, 7, dendritic growth; 8-10, developing crystals within 

 cell; 11, druse in mature parenchyma cell at petiole base. 

 (After F. M. Scott.) 



Proteins as ergastic products occur in crystalline and noncrystalline 

 masses. Perhaps the most familiar protein reserves in plants are the 

 aleurone granules of certain seeds, notably those of cereals, legumes, 

 walnuts, and the castor bean. Such granules may have amorphous 



