ALLIUM CEPA 



195 



are in contact with one another, closing the cavity within until the 

 next younger leaf pushes through it. In the later leaves, the tip 

 of the blade may be pushed through the orifice of the next older 



Fig. 89. Median longisection, except at the bottom, through the plane of phyllotaxy of 

 five-months old stem : B, transection through a perimedullary bundle ; C, cortex ; L, leaf 

 trace; P, pith; R, root trace, X-X, sheath and blade of one leaf. (After Hoffman.) 



leaf while both are themselves enclosed within the sheath of a still 

 older one. (Fig. 89.) 



Hoffman has found that in the growth of the first leaves, the 

 blade attains a considerable length before the sheath begins to 

 elongate appreciably. Growth takes place at about equal rates 

 in all parts of the blade, but the leaf tip is the first part to cease 



