REJUVENESCENCE IN NATURE. 89 



From the vanishing region at the entrance of the 

 hypsophyllary formation, where this separates as inde- 

 pendent, we come to the consideration of that transition 

 in which the disappearance of the leaf-formation is com- 

 monest, to the transition from the hypsophyllary formation 

 to the flower. Here where the most important revolution 

 occurs in the metamorphosis, where the leaf-formation is 

 to return in new arrangement and altered attire, there is 

 most frequently a preparatory total contraction, so that 

 the region of transition into the flower must be desig- 

 nated as the principal break in the metamorphosis. The 

 disappearance of the leaf-formation occurring here may 

 extend simply to a last organ, or over the entire hypso- 

 phyllary formation ; in fact, it may even invade the outer 

 formations of the flower. Of the first case, in which only 

 a final section of the hypsophyllary formation undergoes 

 suppression, we have already seen above a fine example 

 in the Composite with naked receptacles succeeding a 

 fully-developed involucre ; and in the Umbelliferae with 

 umbellules, the outer rays of which arise in the axils of 

 iuvolucellar leaves, while the inner possess no visible 

 bracts. Such cases are more uncommon on racemose or 

 spicate inflorescences with elongated axes, but Castanea 

 and Acalyplia may be mentioned, the spikes of which 

 have perfectly developed hypsophyllary leaves at the lower 

 part, bearing the female flowers in their axils, while the 

 male flowers succeeding upward arise from the axils of 

 abortive leaves. Here refer also the Aroideae, which 

 possess a large, often petaloid, coloured hypsophyllary 

 leaf at the base of the spadix, while no further visibly 

 developed leaves occur upon the spadix. Suppression of 

 the last hypsophyllary leaves is more commonly found 

 when these are situated on a second axial system, than 



normally in a Panicum cultivated in gardens, which I have named P. (Echino- 

 chloa) mirabile. This species, allied to P. stagninum, very frequently presents, 

 besides the three ordinary glumes and the normal palea (deck-spelze) enclos- 

 ing the flower, a second smaller palea, which, like the first, conceals a 

 perfect flower in its axil. 



