TRILLIUM RECURTATUM. 207 



14. The very thin walls of the loose tissue. 



15. The thickened walls of the outer part of the core, 

 and the intercellular spaces at the angles. 



1 6. Draw a portion of these several tissues of the root. 



17. The somewhat irregular row of thickened, slightly 

 colored cells, the bundle sheath, usually with an evident 

 middle lamella in the walls. 



1 8. The fbro-vascular bundle. 



a. Immediately within the bundle-sheath a row of 

 thin-walled cells, the pericambiitm? 



b. The radial rows of large vessels, larger toward the 

 center, smaller toward the periphery. 



c. The intermediate groups of sieve tissue. 



d. The thin-walled cells of the center of the bundle. 

 f. Draw the nbro-vascular bundle and bundle-sheath. 



Make several longitudinal sections through the core of 

 the root ; identify and study 



19. The several tissues seen in transverse section, drawing 

 a few cells of each. 



B. THE ROOTSTOCK (Subterranean Stem). Make a 

 transverse section, mount in strong potassic hydrate, and 

 notice 



1. The row of epidermal cells with brown outer walls. 



2. The parenchyma tissue within, filled with starch, and 

 forming the mass of the rootstock. 



3. Draw a few cells of epidermis, and of adjoining paren- 

 chyma. 



4. The fibro-vascular bundles, cut at all angles, even longi- 

 8 Sometimes absent in old roots by having become permanent tissue. 



