THE DIFFERENTIATION OF THE PLANT-BODY 27 



(fig. 30) ; the vascular bundles of many Monocotyledons 

 are surrounded separately by a sheath of small cells of 

 similar character (fig. 31) ; in Pennisetum (fig. 32, 4) a 

 sheath is developed round the stem in the form of a hollow 

 cylinder which lies between the bundles and the epidermis. 

 More frequent instances occur in which two of the 

 regions in question are strengthened simultaneously. In 

 the stems of Scirpus (fig. 32, 5) there is a development of 

 sclerenchyma round the periphery, and strands occur also 



FIG. 30. LEAF OF Pinus (ONE OF THE CONIFERS) 



e P* epidermis ; hy } layer of sclerenchyma ; en, endodermis ; v.T). vascular 

 bundle ; r.d., resin duct. 



in connection with the bundles. Sometimes these are con- 

 nected by bands of sclerenchyma lying between them. In 

 Fimbristylis (fig. 32, 7) there is a ring of sclerenchyma in 

 the cortex and patches around the periphery, which in other 

 cases are joined like those of the former type. In the stems 

 of Typha (fig. 32, 9) a band of sclerenchyma lies at the 

 back of each bundle, and either a ring or some isolated 

 strands may be found in the cortex. The stem of Juncus 

 (fig. 32, 10) shows these two forms combined together. 



Still more complicated cases show sclerenchyma arising 



