DISTRIBUriON OF SPORES AND SEEDS. 28 1 



nearly horizontal when the seed falls. These fruits or seeds 

 sink from 2 to 30 times as slowly as the same bodies without 

 the wing. Sometimes special floats are used for this purpose, 



Fig. -243.^ Fruits with wings. A , fruits of ailanthus tree (A . g:la.ndulosus\ eacli carpel 

 with dbuble wing. B, fruits of a maple tree, each carpel with a single wing. Natural 

 size. — After Kerner. 



as in dandelion and thistle (fig. 244). Hairs of the most 

 various origin are produced in such numbers and position as 

 to form either parachutes or tangled woolly envelopes to the 

 fruit or seeds (figs. 245, 246). 



399. 4. Distribution by animals. — To secure this there 

 are two general methods observable, (a) The seed or fruit 

 is either adapted for transport by adhering to the body of the 

 animal ; or (U) the seeds are surrounded by edible parts, and 

 at the same time so protected against the digestive juices that 

 they may pass uninjured through the alimentary canal. A few 

 plants are distributed by animals which collect and hide their 

 fruits or seeds (e.g., the squirrels). The adhesion of fruits or 

 seeds to animals, especially to those which are provided with 

 fur, is generally secured either by surfaces made adhesive by 

 the sticky secretion from glandular hairs, or by the develop- 

 ment of outgrowths in the form of hooks or barbed prickles 



