124 AMONG THE WILD FLOWERS. 
with forked hairs, and the heads drooping in 
bud. In cornfields, Centaurea cyanus, Corn 
Blue-bottle, displays its handsome blue flowers ; 
and C. Scaébzosa, Great Knap-weed, on borders 
of fields and banks, with large solitary purple 
flowers; also C. Mzgva, Black Knap-weed, or 
Hard-heads, a purple flower, looking like a 
thistle, but not spinous, very common. 
Lactuca muralis, sometimes called Pren- 
anthes, Wall Lettuce, is a handsome plant with 
dark purplish stalks and leaves, and rather 
small flowers, each of which has five ray florets, 
and looks like a simple flower with five petals ; 
it will erow on the driest wall; there are three 
other species. 
The genus Sonchus, Sow-thistle, has four 
species, of which S. avvenszs, Corn Sow-thistle, 
is the most common, displaying its white downy 
heads all too abundantly, and sowing itself 
widely. Sezecto sylvaticus is a tall species of 
Groundsel, much branched at top, and bearing 
flowers with small revolute rays; it grows in 
dry heathy places. The viscid Groundsel, S. 
viscosus, may be also found, having leaves 
covered with vzsczd, sticky, glandular hairs. 
There are five species of F2/ago, Cudweed ; 
