470 DEGENERATION. 



Although many of the circumstances above men- 

 tioned apply to plants whose structure is habitually 

 rudimentary, there is no reason why they may not, 

 under due restrictions, be applied to plants whose 

 organs are only occasionally defective. 



For further remarks on the subject of Abortion, the reader is referred 

 to the sections relating to suppression, etc., also to Moquin-Tandou, 

 'El. Terat. Veget.,' p. 120; C. Morren, "De I'atrophie en general," in 

 Bull. Acad. Belg.,' t. xviii, 1851, part i, p. 275. 



CHAPTER II. 



DEGENERATION. 



While the terms atrophy and abortion apply in the 

 main to a mere diminution of size, as contrasted with 

 the ordinary standard, degeneration may be under- 

 stood to apply to those cases in which not only is the 

 absolute bulk diminished, but the whole form is altered 

 and depauperated. Degeneration, thus, is the result 

 not so much of a deficiency in growth as of a perver- 

 sion of development. 



Under natural, i. e. habitual circumstances, the for- 

 mation of pappus in place of a leafy calyx may be 

 considered as an illustration of degeneration. It is 

 evident, however, that no very decided Hue of demarca- 

 tion can be drawn between cases of perversion and of 

 arrest of development. 



Formation of scales. These may be mere epidermal ex- 

 crescences, or they may be the abortive rudiments of 

 leaves. Of this latter nature are the '* cataphyllary " 

 leaves which invest the root stocks of so many perennial 

 plants, the perulae of leaf-buds, or the paleae on the 

 common receptacle of composite flowers. Other illus- 

 trations of a like character are to be met with in the 



