REPRODUCTIVE ORGANS. 



117 



FIG. 120. A common tumbleweed ( Cycloloma). 



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 

 " tumble weeds " or 

 "field rollers/' 

 These plants are 

 profusely branching 



Q 



annuals with a sma.ll 

 root system in a 



FIG. 121. The 3-valved fruit of violet discharging 

 its seeds. After BEAL. 



