PLANTS OF THE INDIAN DESEET. 13 



striated. The epidermal cells at the margin have outer walls convexly 

 arched outwards and have both the inner and outer walls thickened. 

 The margins are strengthened by a few collenchymatous cells. The 

 stomata occur abundantly on both the surfaces and are surrounded 

 by ordinary epidermal cells. The guard-cells are elevated and the 

 front cavity is on a level with the surface. The mesophyll is formed 

 of a homogeneous tissue of horizontally elongated polygonal assimila- 

 tory cells. Internal secretory organs are found neither in the leaf nor 

 in the axis. 



The leaves are many-ribbed and the veins of the ribs are vertically 

 transcurrent above and below by collenchyma. The smaller veins are 

 embedded. The vascular bundles of the veins are bicollateral. 



Clothing as well as glandular hairs do not occur on the leaf and 

 axis. 



Structure of the Axis. — The axis is irregularly ribbed, some of the 

 ribs being wing-like. The ribs are strengthened by collenchyma. The 

 epidermis consists of tabular cells with both outer and inner walls 

 thickened. The cuticle is striated. The cortex is composed of chloren- 

 chyma which extends to the ribs. 



A sclerenchymatous pericycle is not developed. The wood is 

 composite and is broader below the ribs. The vessels are small and 

 are arranged almost in complete rows. Interfascicular wood prosen- 

 chyma is little developed. The medullary rays are uniseriate and 

 numerous. The vascular bundles are bicollateral and have two con- 

 tinuous rings of soft bast — one on the outer and another on the inner 

 side of the wood cylinder. The pith is composed of thin-walled cells. 



Oxalate of lime occurs in the form of star-like clusters of acicular 

 crystals in cortical parenchyma and pith. 



(To be continued.) 



