TISSUES AND SIMPLE ORGANS. 



117 



sentially in that it is the epidermis of the root from which the root- 

 cap is developed by centripetal 

 cell-division and branching. 

 In this case the tissue which 

 forms the root-cap bears root- 

 hairs at some distance behind 

 the tip of the root. If we 

 designate the tissue which 

 forms the root-cap of dicoty- 

 ledons as calyptrogen, that of 

 monocotyledons should be 

 called ' ' dermocalyptrogen. ' ' 

 The Helianihus or Brassica 

 type corresponds to 1 a, that 

 of Pisum to 1 /3. 



3. The parenchyma, either 

 the outer layers or the entire 

 tissue, may form the root-cap 

 by the branching of the cell- 

 layers, as in the gymnosperms 

 Juglans regia and Ccesalpinia 

 brasiliensis. 



4. The apical cell (event- 



FIG. 64. Root-tip of Lepidium sativum. 

 ep, Epidermis. (After Schwendener.) 



FIG. 65. From the root-tip of Cytisus racemosus. 

 ep, Epidermis. (After Schwendener.) 



