STRUCTURAL MODIFICATIONS. 



19 



LAW ^.—Each part pre- 

 serves its oim function and 



a characteristic fonm. 



The forms referred to 

 correspond in general with 

 those whirh have been in- 

 di»"ated above. Deviations 

 from this law are caused 

 by Metamorphosis, Ena 

 tion, resulting in the true 

 appenda^ing of 



an 



similar 



organ, 

 of 



the 



exag- 



very similar process 



geration in the growth of a jwirt, retarda- 

 tion in its growth, or its suppression or 



— a 



abortion. With the exception of the firi>t 

 tbf results of those processes will be dis- 

 cussed under the details of the respective 

 parts* 



Metamorphosis is the simulation in form 

 or function, or both, of one organ by an- 

 other. The rose, which normally has but 

 five petals (Fig, 4G), is seen under culti- 

 vation to consist of a dense mass of thorn 

 in many circles, becoming a so-called 

 "double" flower- An oxamimition of the 

 Inner petals of such a flower (Fig. 47) 

 discloses that they are successively 

 smaller and more stamen-like as they 

 stand nearer the stamens, indicating their 

 orig?n through the metamorphosis of the 

 latter, which are fewer in proportion as 

 the petals are more numerous. In another 

 form of the rose, the "Grecu Rose/' the 

 petals in turn appear trnns^trmed Into 

 leareg or leaf-like bodies. Such acci- 

 dtatal or artificial deviations from the 

 normal trnc arc call* d Monstrosities. The 



sepals also frequently present a leafy ap- 

 pearance as an abnormality, or in most 

 species habitually. Even the stamena 

 and carpels frequently display the latter 

 abnormality. In all of these cases the 

 change is from a more complex organ, or 

 one of higher rank, to one of a lower, and 

 is called Retrograde Metamorphosis, or 

 Reversion of Type. Progressive Meta- 

 morphosis also occurs. It is seen in the 

 gradual transformation of bracts, them- 

 selves transformed leaves, into sepals in 

 the Barberry (Fig. 48), and of sopals into 

 petals and petala into stamens (Fig, 49) 

 in the Water Lily. Even stamens may 

 become metamorphosed into carpels and 

 carpels into stamens, one instance being 

 the flowers of the willow, where organs 

 have been seen intermediate in appearance 

 between the two. Cases of abnormal 

 retrograde metamorphosis are very com- 

 mon, and have given rise to a separate 

 department of study known as Teratology, 



Enation and the effects produced by it 

 are well illustrated in one of their forms 

 by the petals of certain genera of the 

 Ranunculaceae. The retention of a drop 

 of nectar at the base of the petal of some 

 species of buttercup is effected by the 

 presence tht-re of a minute scale (Fig, 50), 

 covering over a slight depression. The 

 nectar is partly lodged in this pit, partly 

 held between the petal and the scale. 

 In the Coptis (Fig. 51), a closely related 

 plant, the depression is deepened into a 

 more obvious cavity and the scale is 

 dispensed with, while in the Delphinium 

 (Fig. 52) the former becomes a long tube. 



Although the detailed consideration of 



R 



F^^Si» 



i§'57. 



at»pondages will be taken up In connection 

 with the several organs to which they 

 appertain, we shall here consider a special 

 class of them, called Glands, not only of 



