REPRODUCTION AND DISPERSAL 925 



their color, though green and relatively inconspicuous when immature. 

 Of the showy fruits of this sort some are white (as in the snowberry and 

 mistletoe), others red (as in the holly, bittersweet, and cherry), others 

 blue (as in the red cedar and blueberry), and still others black (as in the 

 blackberry and black haw), or yellow (as in various Solanaceae). 

 Though showy fruits doubtless attract fruit-eating animals and thus 

 facilitate seed dispersal, it is likely that the advantage of such showiness 

 has been overestimated. Probably the animals would find the fruits if 

 they were not highly colored; indeed, some edible fruits, as in Asimina 

 and Ribes Cynosbati, are green at maturity. Furthermpre, species with 

 fleshy fruits doubtless would become dispersed, even if all fruit-eating 

 animals should disappear (see below concerning nut dispersal). Showi- 

 ness, therefore, probably is merely an accompaniment of ripening,' in- 

 dicating the occurrence of certain chemical changes; incidentally they 

 also are of some advantage in that animals thereby are attracted. Some 

 fruits, as the blackberry, are showiest when red and immature, and some 

 showy fruits (as in Physocarpus) are quite dry and inedible. 



Doubtless various large wading birds, such as the herons, carry seeds in the mud 

 that adheres to their feet, thus accounting, perhaps, for the wide distribution of 

 some swamp plants. Fruit-eating animals do not always 

 facilitate dispersal. For example, in autumn, birds feed abun- 

 dantly on the fruits of various plants (such as the ragweeds, 

 sunflowers, and certain grasses, as wild rice), eating the seeds, 

 and thus preventing rather than advancing dispersal. Recently 

 it has been shown that ants play an important part in the 

 dispersal of many small seeds, particularly where the seeds 



have oily appendages which the ants utilize as food. Cer- 



, , , ,. FIG. 1223. A 



tain heavy seeds (such as the nuts and acorns, fig. 1223) , , 



, J ' nut (acorn) of the 



usually are not scattered in any of the above ways; further- y ac ^ oa k / Quercus 



more, they are gathered and eaten in large numbers by squirrels, velutina), partially 

 Occasionally nuts that are carried off by animals are not eaten, enclosed by its cup 

 and thus may germinate, but at best such a means of dispersal (c) t which has de- 

 is rather precarious. veloped from the 



involucre ; note the 



The relative efficiency of the various means of dis- >' bricated * cales 



of the cup (5). 



persal. Three considerations seem to be involved in 

 successful dispersal: the number of disseminules transported, the 

 distance they are taken, and the degree of precision with which 

 they lodge in places favorable for germination and for subsequent 

 development. Some seeds and fruits are not transported at all, the 

 most notable examples being those that ripen under ground, as in 



