472 DEGENERATION. 



Moquin cites in illustration of the first phenomenon 

 the flower of a ViciOf in which the petals were thick 

 and fleshy, like the scales of a bulb ; and of the second 

 the leaves of a Chrysanthemum, which were replaced 

 by small, glossy scales, like those which invest ordinary 

 leaf-buds. Sometimes the entire flower is replaced by 

 accumulations of small, acute, green scales. Cases of 

 this kind, wherein the flowers of a pea and of the fox- 

 glove were replaced by collections of small ovate green 

 scales packed one over the other till they resembled 

 the strobile of a hop, have been already alluded to. 

 Most of these scales are represented as having had 

 other accumulations of scales in their axils. 



Similar collections of scales may frequently be met 

 with in the birch and in the oak, and probably repre- 

 sent abortive leaf-buds. Other cases of a like kind in 

 Gentiana Amarella, where the scales are coloured, are 

 mentioned elsewhere. 



In some kinds of Canvpanula a similar change is not 

 uncommon. 



Formation of hairs, spines, &c. The adventitious produc- 

 tion of hairs is likewise frequently due to an arrested 

 growth, in some cases arising from pressure impeding 

 the proper development of the organ. In other cases 

 the formation of hair seems to accompany the diminished 

 development of some organ, as on the barren pedicels 

 of the wig plant, Rhus Cotinus. A similar production 

 of hair may be noticed in many cases where the de- 

 velopment of a branch or of a flower is arrested, and 

 this occurs with especial frequency where the arrest 

 in growth is due to the puncture of an insect, or to 

 the formation of a gall. In such cases the hairs are 

 mere excrescences from the epidermis. 



Prickles differ but little from hairs save in their 

 more woody texture, but true spines or thorns are 

 modifications either of a leaf or of a branch. Their 

 presence seems often dependent on the soil in which 

 the plants grow, or on other external circumstances. 



