XVI.] THE BEAN PLANT. 471 



d. The root-cap, covering the tip of each rootlet : 

 this is difficult to get whole out of the ground in 

 the bean, but is readily seen by examining the 

 roots of duckweed (Lemna) with 1 inch obj. In 

 the latter plant it consists of several layers of 

 cells forming a cap on the end of the root, and 

 ending abruptly with a prominent rim some way 

 up it. In the bean the root-cap can be well 

 seen by making a longitudinal section of the 

 radicle of the seed. See below, f. 1. c. 



e. Make a transverse section of the main root of 

 a seedling about an inch below its junction with 

 the stem. Note that the whole root is destitute 

 of chlorophyll. Observe with a low power 



u.. The epidermis. 



/?. The wide cortex. 



y. The central vascular cylinder. Note the four 

 xylem-bundles alternating with the same num- 

 ber of phloem-bundles. 



8. In a section passing through the insertion of 

 a lateral root, observe that this arises endo- 

 genously and immediately outside one of the 

 groups of xylem. 



c. The stem. 



1. Erect, green, four-cornered, with a ridge at each 

 angle; not woody; the gradual shortening of the 

 internodes towards its apex. 



2. Cut a thin transverse section of the stem through an 

 internode; note its central cavity, and the whitish ring 

 of fibro-vascular bundles in it, which is harder to 



