REPRODUCTIVE ORGANS 
117 
FIG. 120. A common tumbleweed ( Cyclolomd). 
of pine and catalpa. Plumes and tufts of hairs are devel- 
oped by the seed-like fruits of dandelion, thistle, and very 
many of their relatives, and by the seeds of the milkweed 
(see Figs. Ill, 112, 113, 114). On plains, or level stretches, 
where winds are 
strong, a curious 
habit of seed dis- 
persal has been de- 
veloped by certain 
plants known as 
" tumbleweeds " or 
"field rollers// 
These plants are 
profusely branching 
annuals with a small 
FIG. 121. The 3-valved fruit of violet discharging 
root System in a its seeds.-After BEAL. 
