ITS THEORETICAL STRUCTURE. 



227 



fcot gradation of leaves or bracts into sepals is extremely common. 

 The transition of sepals into petals is exemplified in almost every 

 case Avliere there are more than two rows of floral envelopes ; as in 

 the Magnolia, and especially in the White Water-Lily, various kinds 

 of Cactus, the Illicium, or Star-Anise of the Southern States, and 

 the Calycanthus, or Carolina Allspice, which present several series 

 of floral envelopes, all nearly alike in color, texture, and shape ; but 

 how many of the innermost are to be called petals, and how the re- 

 mainder are to be divided between sepals and bracts, is entirely a 

 matter of arbitrary opinion. In fact, the only real difference be- 

 tween the calyx and corolla is, tliat the fomier is the outer, and the 

 latter an inner series of floral envelopes. Sometimes the gradation 

 extends one step farther, and exhibits an evident transition of petals 

 into stamens ; showing that these are of the same fundamental 

 nature as the floral envelopes, which are manifestly traceable back 

 to leaves. The White Water-Lily (Fig. 344) exhibits this latter 

 transition, as evi- 

 dently as it does 

 that of sepals into 

 petals. Here the 

 petals occupy sev- 

 eral "o'horls ; and 

 while the exterior 

 are nearly undis- 

 tinguishable from 

 the calyx, the in- 

 ner are reduced in- 

 to organs which are 

 neither well-formed 

 petals nor stamens, 

 but intermediate be- 

 tween the two. They are merely petals of a smaller size, with 

 their summits contracted and transformed into imj^erfect anthers, 

 containing a few grains of pollen : those of the series next within 

 are more reduced in size, and bear perfect anthers at the apex ; and 

 a still further reduction of the lower part of the petal completes the 

 transition into stamens of oi'dinary appearance. 



427. By regular gradations, therefore, the leaf may be traced to 



344 



FIG. 344. A sepal, petals, bodies intermediate between petals and stamens, and true sta- 

 mens, of the AVIiito Water-Lily. 



