86 



COMPENDIUM OF GENERAL BOTANY. 



the leaf, as seen in cross-section. Further, there are often special 

 mechanical cells at the margin of the leaf which also assist in pre- 

 venting tearing (SACHS, HABEKLANDT, HINTZ). 



Although the difference between monocotyledons and dicotyle- 

 dons is very great, we must not omit to note the similarities that 

 exist. If we leave out of consideration the cambium, we cannot 

 fail to see the similarity between a rnonocotyledonous and a dicoty- 



FIG. 51. Vascular bundle of Ricinus communis. 



6, Bast ; |/, sieve-tissue or leptome ; g and i, vessels ; c and cb, cambium ; r, parenchyma ; 

 just beyond b a starch-bearing layer (bundle-sheath). (After Sachs.) 



ledonous vascular bundle. The explanations of the figures of 

 the rnonocotyledonous bundles in the text-books of SACHS, HABER- 

 LANDT, FRANK, and in the plates of KNY, are imperfect, since 

 the rather plentiful wood-parenchyma is scarcely, or not at all, 

 mentioned. The tissue between the two large vessels (g) and the 

 ring- vessels (, r in Fig. 50), near the sides between the two 

 larger vessels, are in part wood-parenchyma, in part thick-walled 



