DISTRIBUTION OF SPORES AND SEEDS. 367 



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 

 (figs 412, 413, 414, 415). A few water animals and wading 

 birds distribute seeds which 

 happen to fall into the mud 

 by the adhesion of this mud 

 to their bodies. 



The fleshy fruits with edible 

 parts are usually colored to 

 attract the notice of the fruit- 

 eating animals. Seeds which 

 escape crushing by the teeth or 

 grinding in the gizzard are apt 

 to be in condition to germi- 

 nate when voided. The seeds 

 of the mistletoe are separated 

 from the pulp of the berry by 

 the birds which eat them, 

 and, sticking to the bill, are 

 wiped off on the branches 

 of trees, where they germi- 

 nate. 



The adaptation of plants to 

 any one of these agents of 

 distribution is likely to be more or less effective with other 

 agents. For example, the tufts of hairs which increase the 

 buoyancy of the seed in air would be equally effective 

 should the seed chance to alight upon water, or they may 

 suffice to entangle the seed in the fur of animals. 



494. Adaptations for germination. — Adaptations for dis- 

 tribution not infrequently also secure, advantage in germina- 

 tion. It is important for many seeds that they be anchored 

 to the ground when they have once been transported, so that 



Fig. 414. 



Fig. 



4i5- 



Fig. 



414. — A, cluster of fruits of Spanish 

 needles (Bidens bifiinnata). B, a single 

 fruit enlarged, showing barbed awns, rep- 

 resenting the calyx lobes, by which it ad- 

 heres to animals. A , natural size ; B, 

 magnified 2.^ diam. — After Kerner. 

 Fig. 415.— Fruit of cockle-bur (Xanthium 

 strumarium), halved, showing two seeds, 

 the upper of which usually germinates a 

 year later than the lower. Natural size.— 

 After Arthur. 



