FORM OF THE PL ANT- CELL. 



were heaped together, a row of stronger, thicker, and longer cells are 

 found (tig. 47.)-* 



During this time the longitudinal parenchyma-cells belonging to the 

 vascular bundles, and which either surround them, or form a great bundle 

 both before and behind, have their walls strongly thickened, so that the 

 unchanged vascular bundles are rendered much more apparent in the 



* See Mohl de Palmarum Structura, where there are many drawings of mono- 

 cotyledonous vascular bundles, but which do not express strongly enough the above 

 peculiarity. 



47 Successive closed vascular bundles from the petiole of Musa sapientum, from a 

 horizontal wall between two air-passages near to the under surfaces of the petiole. 

 A, A transverse section. B, A longitudinal section of the same. The arrow denotes 

 the direction from the upper to the under surface of the petiole, a, The cambium 

 cells ( Vasa propria of Mohl). 



