REPRODUCTIVE ORGANS. 



117 



Fig. 120. A common tumbleweed ( Cyclolomd). 



of pine and catalpa. Plumes and tnfts 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, 

 w here w i n d s are 

 strong, a curious 

 habit of seed dis- 

 persal has been de- 

 veloped by certain 

 plants known as 

 " tumbleweeds " or 

 ' ( fi e 1 d 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. 



