140 ANATOMY OF STEM, ROOT AND LEAF 



Ex. 68. — Make thin transverse sections of a wheat or barley stem. Ex- 

 amine with a low power : observe the thick walls of the epidermal and 

 subjacent ground-tissue cells ; note also the scattered vascular bundles and 

 hollow centre. 



Sketch a single vascular bundle as seen under a high power ; note especially 

 the absence of cambium. 



Take two or three pieces of barley or wheat straw each about a quarter of 

 an inch long, and press them flat. After placing them together, hold them 

 in your fingers and cut longitudinal sections, some of which will pass wholly 



Fig. 72. — I. Young 

 root of !i pea. /: Root- 

 hairs of the piliferous 

 layer ; c root-cap. 

 tTwice natural size. ) 



2. Transverse section through a young root of a pea near h in i. 

 h Root-hairs ; c cortex ; p piliferous layer ; e endoderniis : n pericycle ; 

 7U wood strand; jrits protoxyleui ; d bast strand. (Enlarged 48 dia- 

 meters.) 



or in part through a vascular bundle. Examine the sections first with a low 

 and then with a high power ; make sketches of the epidermis, thick and thin 

 walled ground-tissue, and annular or spiral vessels of the wood. 



^; THE ROOT. 



The outermost part of a young root, corresponding in position 

 with the epidermis of the stem, consists of a single layer of cells 



