StetH and Root Structures 



n 



A tissue is a group of cells which have had a common 

 origin, have developed in a similar manner so as to have the 

 same appearance, and have the same work to do : for example 

 we speak of the epidermal tissue, ground tissue, vascular tissue, 

 cortical tissue. At the apex of the stem the cells are alike 

 forming one tissue — primordial meristem. Close behind 



SI D P 



Fig. "^. — 7'he growing point (liighly magnified) of the stem of Finns 

 syh'estfzs, D, dermatogen ; P, periblem and plerome ; SI, scale leaf (highly 

 magnified). (Photo-micrograph by Flatters, Milbourne. & McKechnie. ) 



the tip, this tissue shows a change : three tissues may be found 

 — (a) the dermatogen {Sep/xa, skin ; yun'dii), I bring forth) or 

 protoderm (-n-piuTo?, first ; ?,ep/.m, skin), (/') procambial strands, 

 ((■) ground meristem. 



(a) The dermatogen divides by walls in two directions at 

 right angles to the surface walls, and, as the derivation of the 

 word indicates, forms the epidermis. 



(/') Farther down the stem, the procambial strands elongate 



