MODES OF PLANT DISTRIBUTION. 303 



parent. Thus the fruit of the hura crepitans or monkey's 

 dinner-bell tree explodes when ripe with a loud report, scatter- 

 ing the seeds far and wide. Every one is familiar with the 

 peculiarities of the common touch-me-not and the squirting 

 cucumber. Some of the fungi, as the puff-balls and the spor- 

 angia of many ferns, burst when ripe with considerable elastic 

 force, and so spread their minute spores to considerable dis- 

 tances. Nevertheless, curious as these contrivances are, they 

 are of comparatively little importance in the general work of 

 plant distribution. 



Finally, plants are scattered over extensive portions of the 

 earth's surface by animals in a manner often apparently acci- 

 dental ; Nature having furnished many seeds and fruits with 

 hooks and claws or with a viscid covering, by which they become 

 attached to moving objects and are carried often far from their 

 native habitats. 



Familiar examples of plants thus furnished are the burdock, 

 the clot-burr, the burr-marigold, and the bush trefoil. The her- 

 bivorous animals, like the buffalo, the antelopes, wild oxen and 

 wild horses, which often range over a wide territory, are the most 

 efficient accidental distributors of plants. 



Birds also often disseminate the stones of small drupes and 

 the hard seeds of berries which are unaffected by their digestive 

 organs, and a few birds as well as many small quadrupeds have 

 a habit of storing up acorns and other nuts and seeds, which not 

 unfrequently are by this means brought into favorable localities 

 for germination. 



The influence of man in modifying Nature's mode of distrib- 

 uting plants is very great and constantly increasing. The de- 

 struction of forests, the draining of swamps, the introduction of 

 new plants for cultivation over millions of acres, all tend to the 

 eradication of existing wild species, and the substitution of a 

 much smaller number of higher value. Of the hundred thou- 

 sand species of flowering plants known to botanists, hardly one 

 hundred are of much importance to agriculture, and probably 

 not more than a thousand are of any consequence in horticul- 

 ture for the production of either flowers, fruit or vegetables. 

 The evident tendency of scientific culture is towards an increase 

 of hybrids and cross-breeds, rather than to the elevation or 

 acclimatization of new species. The apple, so attractive in Eden, 

 still has its charms for us, and we are still trying with encour- 



