174 



BEi.JXXERS' BOTANY 



fruits are agreeable as human food, arid some of them 

 have been greatly enlarged or " improved " by the arts of 

 the cultivator. The seeds arc usually indigestible. 



Burs. — Many seeds and fruits bear spines, hooks, and 

 hairs, which adhere to tlie coats of animals ajid to c/ot/iinj^. 

 The burdock has an involucre with hooked scales, contain- 

 ing the fruits inside. The clotbur is also an involucre. 

 Both are composite plants, allied to thistles, hut the 



whole head, rather than the separate 

 fruits, is transported. In some com- 

 posite fruits the pappus takes the 

 form of hooks and spines, as in the 

 " Spanish bayonets " and " pitch- 

 forks." Fruits of various kinds are 

 known as "stick tights," as of the 

 agrimony and hound's-tongue. Those 

 who walk in the woods in late sum- 

 mer and fall are aware 

 that plants have means 

 of disseminating them- 

 selves (Fig. 252). If it 

 is impossible to iden- 

 tify the burs which one 

 finds on clothing, the seeds may be planted and specimens 

 cf the plant may then be grown. 



Suggestions. — 174. What advantage is it to the plant to have 

 its seeds widely dispersed? 175. What are the leading ways in 

 which fruits and seeds are dispersed? 176. Name some explosive 

 fruits. 177. Describe wind travelers. 178. What seeds are car- 

 ried by birds? 179. Describe some bur with which you are 

 familiar. 180. Are adhesive fruits usually dehiscent or indehis- 

 cent? 181. Do samaras grow on low or tall plants, as a rule? 

 182. Are the cotton fibres on the seed or on the fruit? 183. 

 Name the ways in which the common weeds of your region are 

 disseminated. 184. This lesson will suggest other ways in which 



Fig. 252. — Stealing a Ride. 



