NATURE OF PLANTS 



39 



These cells are developed as a result of the stimulating influence 

 of light (Fig. 26). Leaves growing in the deep shade show little 

 indication of palisade structure. The compact arrangement of 

 these cells prevents to a large degree the access of the hot, dry 

 air and consequently loss of water is less than would be the 

 case if the cells were separated by intercellular spaces. Shade 



Fig. 26. Fig. 27. 



Fig. 26. Section of a leaf of Rhododendron. Note the compact palisade 

 tissue which enables the plant to withstand drying winds. 



Fig. 27. Section of a leaf of skunk cabbage, Spathyema. Note the poorly 

 developed palisade tissue and the loose arrangement of the cells of this plant 

 which lives in moist, shaded places. 



and moisture loving plants are not obliged to conserve the amount 

 of water received and these two forces, feeble light and moisture, 

 produce a larger and looser arrangement of tissues which is 

 favorable to an interchange of gases and transpiration (Fig. 27). 

 Particularly is this noticeable in aquatics as in the water lilies 

 and many rushes, etc., where the tissue is loose and spongy 

 and permits a ready circulation of gases from the leaves to the 

 roots and to all parts of the plant body even when submerged. 

 This loose arrangement of tissues also renders water plants very 

 buoyant and consequently they are less liable to injury from 



