128 



PLANT ANATOMY 



¥\g. 28.— Hyoscyamus niger. Cross section of seed showing « 

 cells, end. Endodermis. c. CotyleUuns. «. isolated aleiirone grains 



enlarged and 

 (Tschirch). 



modified epidermal 



In roots they are generally simple and 

 are called root hairs, are somewhat elon- 

 gated and have very thin walls and are 



trie-homes are of almost every conceiv- 

 able variety. Some hold no secretion, 



and are called hairs in the narrow sense 

 situated a little behind the root cap and of the word, and others contain secre- 



Fig. 29.- Root Hairs. 



limited to a small area. Their function 

 is mainly that of absorption of moisture 

 holding mineral salts in solution. 

 In stems and leaves and flowers the 



tions and are called glands. These 

 hairs, or papillae, as they are called when 

 in floral petals, serve as a means of iden- 

 tification in Viola flowers, where they 



