472 DEGENERATION. 
Moquin cites in illustration of the first phenomenon 
the flower of a Vicia, 1m 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- 
elove 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 Campanula a similar change is not 
uncommon. 
Formation of hairs, spines, &—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. 
