REPRODUCTIVE ORGANS. 



117 



Fig. 120. A common tumbleweed (Cydohmufy. 



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. 111. 112, 113, 111). 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 roller- 

 These plants are 

 profusely branching 

 annuals with a small 



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



root system in a ite 8e ed B .-After bbal 



