Il6 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



Fruits destined to have their contained seeds disseminated by 

 Mammals tend to be less conspicuous than those primarily intended 

 to attract Birds, e.g. when flying. And even as Birds will devour 

 the attractive part of a fruit and scatter the seeds without ingestion, 

 so will many Mammals do to large fruits. Arboreal Mammals, such 

 as Monkeys, commonly do not eat fruits when they gather them, 

 but quietly remove them to a distance — apparently to avoid being 

 robbed. If they drop a fruit they do not pick it up, but go on to 

 another. Moreover, such types as Squirrels make large winter 

 caches that may involve extensive transportation and frequently are 

 not eaten in the end. These and many other activities of Mammals 

 can help plant dispersal within continental confines. 



Because of their frequently furrv coats, Mammals tend to be more 

 commonly effective than Birds in the ectozoic transportation of 

 adhesive fruits, such as those with hooks or other devices for attach- 

 ment. Many fur-coated Mammals wander extensively, or travel far 

 on migration, some even crossing wide tracts of sea-ice in the Arctic. 

 Apart from being furnished with obviously effective hooks or spines, 

 some seeds and fruits adhere to animals by viscid glands, gummy 

 exudations, or owing to their wholly sticky nature, while the spikelets 

 of many Grasses do so by jagged parts or minutely toothed awns. 

 Many other seeds and fruits which are normally wind-dispersed, 

 will adhere to animals by entanglement or sticking of their hairs or 

 plumes especially when wet. There is, indeed, no lack of means or 

 instances of such dispersal, as inspection of one's clothes at the end 

 of an autumn walk in a temperate woodland will show. Moreover, 

 it should be remembered that animals, like plants, are selective of 

 habitat, and tend to keep, as Birds tend to alight, within a single 

 habitat-range — so increasing the chances a disseminule would have 

 of coming to rest in a place suitable for germination and successful 

 establishment. For instance, the rocky ridges and ravines in boreal 

 regions that are inhabited by such birds as Snow Buntings and 

 Ptarmigan, which commonly ingest seeds and migrate from one to 

 another such area, afford numerous habitats for open-soil Saxifrages 

 and Sandworts which may be lacking in intermediate areas. 



(c) Lower animals. Although most of the Reptiles of the present 

 era are carnivorous, some feed on fruits and may disseminate them. 

 More important in this respect are freshwater Fishes, many of which 

 are vegetable feeders that swallow the seeds of aquatics and semi- 

 aquatics, and some of which can migrate overland, usually through 

 wet Grass. Of a wide range of seeds or fruits of aquatic plants, such 



