CAPSELLA BURSA-PASTORIS. 229 



with a high power, and note 



/. A peripheral region, consisting of the epidermis, 8 



and a few layers of hypodermal cells. 

 g. A median region of colorless cells, the cortex. 

 //. Within this a single row composed of somewhat 

 smaller, more closely packed cells, the bundle sheath. 

 i. The space inclosed by the sheath entirely occupied 

 by \\\Q fibro-vascular region, in which note 

 i. The two xylem masses, placed with their inner 

 ends of larger cells in contact, thus dividing 

 the region into similar halves (binary]. 

 ii. The two phloem masses, placed right and left 



of the xylem. 



iii. A limited amount of parenchyma, separating 

 the xylem and phloem portions from each 

 other, and both from the bundle sheath. 

 j. Draw the whole section. 



A series of ^transverse sections of larger and larger root- 

 lets will show secondary changes, characteristic of dicoty- 

 ledons, up to 



2. The main shaft. Make a transverse section, examine 

 with a low power, and note 



a. The entire disappearance of epidermis. 



b. The cortical parenchyma. 



c. The fibro-vascular cylinder. 

 Using a high power, note 



d. The cortical parenchyma arranged in radiating lines, 

 from the tangential and radial division of its 

 meristem cells. The outer layers may be com- 

 posed of thin-walled, close set, squarish cells, cork ; 

 within which are often other layers of larger cells, 

 much distorted from the pressure under which the 



5 The epidermis may have disappeared even in a very small rootlet. 



