60 ELEMENTARY BOTANY. 



tion. Their light dissected parachute or fluffy ball is the 

 modified form of the calyx, called the pappus. The wing- 

 like bract doubtless renders the fruit cluster of the Basswood 

 more buoyant and transportable by the wind. Many fruits 

 have barbs, hooks or prickles by which they lay hold of ani- 

 mals or the clothing of man and in this manner are often car- 

 ried great distances. Such are the fruits of the Beggar-ticks 

 {Bidens), Tickseed (Coreopsis), Tick-trefoil {Meibomia), Bur- 

 grass (Cenchrics), etc. In the Burdock the involucral scales 

 are hooked and the whole head of fruit is often carried from 

 the plant on which it grew. The prickly fruit of the Cockle- 

 bur also represents an involucre and its assistance in distribu- 

 tion is similar and very eSectual. 



6. Fleshy and edible fruits are, it is true, often eaten and 

 wholly destroyed; it might therefore seem that the produc- 

 tion of an edible part would be a detriment to seed-disper- 

 sion. But in very many cases the seeds escape uninjured. 

 Indeed the importance of such fleshy or edible portions in 

 effecting the distribution of the seed is such that we may 

 regard that as their proper and only function. Many seed- 

 coats are so firm as to resist for a long time the action of 

 water. The seeds may therefore germinate after being trans- 

 ported long distances by river and ocean currents. In several 

 cases, for example. Witch Hazel and Touch-me-not, the pods 

 burst in such a way as to throw the seeds some distance. 



7. The seeds of pods that break open at maturity are in 

 some cases furnished with appendages that aid in the dissem- 

 ination. Those of the Trumpet Creeper and Catalpa have 

 conspicuous thin wings. In the former these entirely sur- 

 round the seed ; in the latter they extend mainly from the 

 two ends and terminate in a hairy fringe. In the Milkweed 

 and Epilobium each seed is surmounted by a tuft of long deli- 

 cate hairs which are very efficient aids to its distribution. 

 The Cotton plant produces in a dehiscent pod, seeds that are 

 completely covered with very long hairs, which constitute the 

 cotton of commerce, and which for the plant are important 

 contrivances for seed distribution. Seeds often lie dormant 



