84 COMPOUND ORGANS OF PLANTS. 



Decandolle considers that the sheathing leaves of endogenous 

 plants which are not furnished with a distinct limb, are only 

 expanded petioles. The leaves of the Hyacinth, and Iris 

 versicolor, or common blue flag of the pools, are of this nature. 

 Such leaves are sometimes met with even in the higher order 

 of exogenous plants, as, for instance, Ranunculus flammula or 

 Spearwort crowfoot, a common aquatic plant. 



Sometimes the edges of the lamina or blade cohere together, 

 producing still stranger modifications of leaf structure. It is 

 well known that the parts of plants which grow closely 

 together, are apt to become coherent. Accidental unions of 

 this kind amongst the leaves of plants are of common occur- 

 rence. In some species these unions occur after the plant is 

 considerably grown, as in the garden honeysuckle, the upper 

 leaves of which usually cohere together by their bases, owing 

 to their sessile character, and form what botanists call a connate 

 leaf. So also, the numerously crowded and closely compact 

 leaves, constituting the calyx or cup of the Marygold or Holly- 

 hock flowers, will be found to be more or less united with each 

 other. In other instances, where the cohesion of the leaves 

 with each other or with the stem is of constant occurrence in 

 every stage of vegetable development, this union appears to 

 take place at a much earlier period. In this case, whilst the 

 plant lies folded up within the seed and its texture is yet deli- 

 cate, the numerous vessels of its organs which are thus brought 

 into close contact anastomose ; that is, run together or unite with 

 one another by means of the elaborated juices which nourish 

 them, thus producing those cohesions of the parts of plants which 

 are visible in their after developments. 



If these views be correct, they will serve to explain the 

 nature of the hollow leaves of Sarracenia purpurea, or the side 



