9MPOSITE FAMILY COMPOSITAE 
SPINY-LEAVED SOW THISTLE 
Sonchus asper (L.) Hill 
This plant is a native of Europe but it is widely distributed 
nearly all cultivated parts of the earth. Although it must be 
assed as a weed, it is a very showy and beautiful one when 
the pale yellow flowers are in 
bloom from May to late autumn. 
Like many other members of 
the Composite family this species 
has flowers which open only when 
the sun shines. 
It is an annual with fibrous 
roots. The stem is 1-10 feet high 
and not much branched. It is 
leafy toward the base but much 
less so toward the top. The leaves 
usually have few lobes and some- 
times none, but they are very 
spiny toothed. The lower and 
basal are petioled, whereas the 
upper are clasping and with basal 
earlike lobes. Stem and leaves con- 
tain an abundance of milky juice. 
The blooming season is May 
to late autumn. The heads are 
several and often numerous. The 
volucre is more or less bell shaped and usually becomes thick- 
ed at the base and more or less cone shaped when old. The 
acts are smooth and arranged in several series, the outer ones 
ccessively smaller. The receptacle is flat and naked. The 
rollas are strap shaped and 5-toothed at the end. Each of the 
it and margined akenes, 3-nerved on each side but otherwise 
1voth, has a very abundant pappus of soft white bristles. 
The Common Sow Thistle, Sonchus oleraceus L., is very similar 
the spiny-leaved species, but the leaves are usually more lobed | 
id not spiny, and the akenes are longitudinally fine ribbed and 
‘inkled crosswise. The plant is a common weed in most cultivated 
rts of the world except the extreme north, and has been naturalized 
this country from Europe. 
~ 388 
