60 EET. G. HE>"SLOW HOMOLOGY AND 



Y. ApPEJ^^DICIJLAR SxRtrCTTJEES — E.EPEODTJCTIVE. 



The floral-leaf Region. — That all the parts of a flower may be 

 regarded as "metamorphosed leaves," or at least as homologous 

 with leaves, has long been recognised and adopted by botanists 

 as a fundamental principle of floral structure. The changes often 

 assumed by the various floral organs may be regarded as retrogres- 

 sive or progresnve respectively. Under the former heading are 

 such metamorphoses whereby the organs affected approximate to 

 a leaf-type, either directly, or are represented, as it were, by a 

 succession of stages. 



Thus the pistil may assume a staminal character in some flowers, 

 by bearing anthers or by producing pollen within the ovules. It 

 may be more or less petaloid, or the carpels may be actually re- 

 placed by perfect petals, as in " double " flowers ; or lastly it may 

 be more or less foliaceous. 



Stamens may be similarly petaloid as in double flowers. They 

 may be sepaloid and virescent or foliaceous as well."^' 



Petals and sepals may both change their normal characters, 

 and become vir'escent or even converted into true and perfect 

 leaves. 



The pistil is normally virescent in most flowers, but becomes 

 foliaceous in the Alpine strawberry, the green rose, the double 

 cherry, and monstrous states of Trifolium repens. 



The ovules may be more or less leaf -like, as in the above examples 

 and in mignionette, Cruciferce, etc. 



The stamens may be viix'scent as in the green rose, in which they 

 also pass by ti ansitional stages into a more or less truly foliaceous 

 character. In several other plants the change has been observed. 

 In a Petunia the stamens were \-irescent, while the connective only 

 was foliaceous. f 



The corolla has often been obsei-ved to be virescent or foliaceous. 

 Thus in the green I'ose, Alpine strawberry. Petunia above 

 mentioned. Primula, and some Lahiatce. 



The sepals not unfrequently are foliaceous in the primrose, in 

 Anemone, Ranunculus, and roses. 



Lastly, bracts become foliaceous in plantains, Primula, and in the 

 involucres of Compositce and Wmbell/ferce. 



Homologies and Changes of the external Floral Organs. Calyx. 

 — Sepals may be homologotis, — 1. with the petiole of a leaf, as is 

 obviously the case in the rose, where the leaflets of the blade are 

 represented in a rudimentary condition. In Pedicularis the blades 

 appear as a minute fiinged apex to the sepals. In Ranuncuhis, 

 Potentilla, and probably in the majority of instances, the broad 

 base of the petiole is the only part present. 



2. The sepals maybe the blades, as in Caltha and Eranthis, where 



* Virescent, when they are green only, but retain their normal form ; foliaceous, 

 when the form is changed into that of a leaf as well. See ' Eull. de 1' Academic 

 Eoyale de Belgique,' tome xvii, part 2, pi. p. 131. 



t ' Teratology,' p. 254, fig. 134. See also tigs. 135 and 136. 



