174 FIELD OATS. 



Strip off the cortical portion of one of the large secondary 

 roots. Notice 



10. The slender, strong fibre-vascular axis which remains. 



Examine some plants three or four days old, which have 

 been grown on the surface of wet blotting paper. Note 



11. The position of roots and stem with respect to the 

 grain. 



12. The abundant root-hairs. Notice their relative length 

 on different parts of the root, and where absent. 



13. The opaque tip of the root covered by the conical root- 

 cap. 



C. THE STEM. Notice that it is completely encased by 

 the sheathing bases of the leaves. Uncover a portion of 

 the stem by removing one of the leaves and its sheath, and 

 note 



1. Its shape, and polished surface. 



2. Its nodes and internodes. Bisect the stem longitudinally 

 through a node and a portion of an internode. Note 



a. The solid node forming a partition between the 

 cavities of the internodes. 



b. Draw. 



Look through the split stem at a bright light, and note 



3. The numerous threads, traversing the stem lengthwise, 

 the fibro-vascular bundles. 



Cut a transverse section and examine by transmitted light, 

 and note 



4. A very firm, more opaque external layer, the cortical 

 layer. Notice its variable thickness. 



5. In the cortical layer, pairs of darker spots. These are 

 clusters of chlorophyll-bearing cells. 



