HISTOLOGY 



39 



The upper and the lower surfaces of the leaves of many grasses 

 are more or less even, but in the case of a few grasses the upper 

 surface consists of ridges and furrows, instead of being even. In 

 the leaves of Panicum repens and Eragrostis Willdenoviana the upper 

 surface is wavy and consists of shallow furrows and slightly raised 

 ridges. But in the leaves of Aristida setacea and Panicum fluitans 

 the furrows are deeper and the ridges are more prominent. In 

 Aristida setacea the ridges are fiat-topped and they are rounded 

 with broad furrows in Panicum fluitans. 



The epidermis covering the leaves consists of elongated cells 

 with plane or sinuous walls, various kinds of short cells intercalated 



Fig. 62. — Upper epidermis of the leaf 

 Panicum Isachne. x 200 



I. Cells overlying the veins ; 2. cells 

 overlying the furrows; 3. stomata. 



Fig. 63. — Lower epidermis of the leaf 

 Panicum Isachne. x 200 



1. Cells overlying the veins ; 2. cells 

 overlying the furrows ; 3. stomata. 



between the ends of long cells, motor-cells and stomata. Hairs of 

 different sorts occur as out-growths of the epidermis. The rough- 

 ness of the surface of the leaves of grasses is due to the presence 

 of very minute short hairs borne by the epidermis. In most cases 

 these short hairs are found in regular rows. Although the epider- 

 mis is more or less even in the leaves of several grasses such as 

 Panicum repens, P. flavidum and EriocMoa polystachya, it is wavy or 

 undulating in the leaves of a few grasses. For example, the upper 

 epidermis in the leaves of Panicum fluitans is undulating as it 

 follows the contour of the ridges and furrows. 



The epidermal cells have even surfaces in the leaves of most 

 grasses but in some they bulge out. In the leaves of Panicum 

 flavidum the cells of the lower epidermis are quite even, whilst 

 those of the upper epidermis bulge out. The cells of both the 

 upper and the lower epidermis are distinctly bulging out in the 



