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, Haberlandt, Hintz). 



Altliough tlie 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; y, sieve-tissue or leptome ; g and «, vessels; c and rt camhium;r^p^^^^ 

 just beyond 6 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, Habee- 

 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 tlie 

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

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



