TISSUES AND SIMPLE ORGANS. 



117 



sentially in tliat 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 Ilelianthus or Brassica 

 type corresponds to 1 o', that 

 of Pisuin to 1 /?. 



3. YixQiKirenchyma^ either 

 the outer layers or the entire 

 tissue, may form the root-cap 

 by the branching of the cell- 

 layers, as in the gymnosj^erms 

 Juglans regia and C(xsalpinia 

 hrasiliensis. 



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.) 



