356 ORGANOGRAPHY. 



flower, as in certain species of Epacris, or beyond the fruit 

 (^fig. 762), and becomes a true branch bearing leaves. 



Various other examples might be adduced of the entire trans- 

 formation of the floral organs into more or less perfect leaves. 

 Thus in the Common White Clover, the parts of the flower are 

 not unfrequently found in a leaf-hke state. A similar condi- 

 tion has also been observed in monstrous Strawberry flowers, 

 &c. In fact, no one can walk into a garden, and examine 

 cultivated flowers, without finding numerous instances of tran- 

 sitional states occurring between the difl^erent organs of the 

 flower, all of which necessarily go to prove their common origin. 



Wlien a sepal becomes a petal, or a petal a stamen, or a 

 stamen a carpel, the changes which take place, are said to 

 be owing to ascending or direct metamorphosis. But when a 

 carpel becomes a stamen, or a stamen a petal, or a petal a sepal, 

 or if any of these organs become transformed into a leaf, this is 

 called retrograde or descending metamorphosis. 



We have thus proved by the most conclusive facts, that all 

 the organs of the flower are formed upon a common type 

 with the leaf, and differ only in their special development, or, 

 in otlier words, — that they are homologous parts. Hence a 

 flower-bud is analogous to a leaf-bud, and the flower itself to a 

 branch the internodes of wliich are but shghtly developed, so 

 that all its parts are situated in nearly the same plane ; and, as 

 flower-buds are thus analogous to leaf-buds, their parts are also 

 necessarily subject to similar laws of development and arrange- 

 ment, and hence a knowledge of the latter gives the clue to that 

 of the former. The symmetrical arrangement of the parts of the 

 flower arising from their being homologous parts with the leaves, 

 will be described in the next section, together with the various 

 causes Avhich interfere to prevent or disguise it. 



Section 8.— Symmetry of the Flower. 



The term symmetry has been variously understood by dif- 

 ferent authors. As properly applied, a symmetrical flower is 

 one, in wliicli each whorl of organs has an equal number of 

 parts, or where the parts of one whorl are multiples of those of 

 anotlicr. Thus in some species of Crassula (Jig. 763), we 

 liave a symmetrical flower composed of five sepals, five |)ctals, 

 five stamens, and five carpels; in Sedum (Jig. 764), we have 

 five sepals, five petals, ten stamens in two rows, and five 

 carpels ; in the Flax, we have five sepals, five petals, five 

 stamens, and five carpels, each of which is ])artially <livided 

 into two by a s])urious dissepiment (Jig. 603); in the Circaa 

 {Jig. 765), we liave two orjzans in each whorl; in the Kue 

 Ijigs. 564 and 596), we have four or five sepals, four or five 



