TRILLIUM RECUR VA TUM. 209 



a. The thickness of the different walls. 



b. Draw. 



5. ^^ parenchyma of the center of the stem. Note 



a. The shape of the cells. 



b. The thinness of the walls. 



c. The large intercellular spaces, 

 if. Draw. 



6. 'Y\\z fibro-vascular bundle. Note 



a. r Y\\z phloem, consisting of angular cells of various 

 sizes; the smaller, conducting cells or bast paren- 

 chyma, the larger, the sieve tissue. 



b. The xylem, in the smaller bundles of less area than 

 the phloem, but in larger bundles greater, and 

 spreading out on either side the phloem, until, in 

 some cases, it entirely surrounds it.' It is made 

 up of 



i. The vessels of various sizes, and 



ii. Interspersed among the vessels and extending 



out on the axial side, rather angular cells, the 



wood parenchyma. 



7. The absence of meristem cells between xylem and 

 phloem, thus forming a closed bundle. 



8. Draw a small and a large bundle. 



Take a longitudinal section through the center of the 

 stem and notice 



9. The several tissues seen in transverse section. 



a. The epidermal and hypodermal tissues. Draw. 



b. The central parenchyma. Draw. 



3 Forming the external sheath (Prantl and Vines, Text-book, p. 58), 

 which is probably but a special development of the surrounding cells of 

 the fundamental system. 



