THE SPERMAPHYTES. 



223 



of the apical bud and radicle in seedlings from a few days 

 to some weeks old. 



3. Make a thin, median longitudinal section through 

 the developing radicle of a seedling. Study the loosely 

 arranged cells of the older portion of the rootcap at the 

 very end of the root ; above these are more compact and 

 regularly' arranged newer cells of the rootcap. Just 

 above these at the apex of the root proper is the growing 

 point of the root. Pro- 

 ceeding from the grow- 

 ing point, study the 



differentiation of the 

 cells for a short dis- 

 tance back into the root. 

 Notice particularly col- 

 umns of broad, horizon- 

 tally flattened cells. The 

 horizontal partitions in 

 these cells will eventu- 

 ally break away, and the 

 columns of cells will be 

 transformed into a ves- 

 sel with long cylindri- 

 cal segments. Find the 

 origin of the secondary 

 roots which, in median 

 sections, appear as dis- 

 tinct circular masses at 

 the junction between the 

 root and the stem. Fol- 

 low up the stem and lo- 

 cate developing leaves. 



4. Cut transverse sections of the stem. Mount in 

 Schultze's solution. Describe the arrangement of the 

 fibrovascular bundles. Are they definitely placed as re- 



FIG. 142. Fibrovascular bundle of Indian 

 Corn, Zea mays. Transverse section, as 

 seen under high power. 0, P, P, cells 

 of the ground parenchyma. The tissue 

 represented by thick dark-walled cells is 

 the bundle sheath ; E, E, pitted vessels ; 

 F, an annular vessel; A, spiral vessel; 

 L, empty space produced by the tearing 

 apart of the tissues in consequence of 

 rapid growth ; H, H, sieve tissue consti- 

 tuting the bast or phloem portions of the 

 bundle ; E, E, A, and F are the main ves- 

 sels of the xylem. The lower part of the 

 figure was situated towards the center of 

 the stem. (X 500.) 



