220 EXPERIMENTAL GENERAL SCIENCE 



by using them one may be understood wherever scientific men 

 are found. 



186. Distribution. Evidences of organic life are everywhere 

 present on the earth. -The shallow waters teem with aquatic 

 animals and plants, other forms creep or walk on the soil, or 

 burrow into it, while still others are rooted in the soil. Other 

 forms float in the air or move through it by their own efforts. 

 The simplest living things are most widely distributed. They 

 swarm in all soils and are to be found on mountain tops, in 

 the arctic regions, and in the oceans depths. Inorganic sub- 

 stances on the globe are usually distributed in a haphazard 

 way, but the distribution of living things depends so much on 

 temperature, pressure, moisture, and light, that there are 

 usually pretty definite limits to the range of each species. 

 Oceans, deserts, mountain ranges, and extensive forests, 

 frequently act as barriers to the spreading of a species in cer- 

 tain directions, and for this reason the plants or animals of 

 distant lands are seldom identical, though the flora (plants) 

 and fauna (animals) of the two regions may contain many 

 related species. Living things are more or less adapted to the 

 places in which they live, and cannot survive as well in any 

 other, owing to the differences in temperature elevation and 

 the like. A few may be adapted to other regions by making 

 new adjustments to their surroundings. This is known as 

 acclimatization. The flora and fauna change more rapidly as 

 one travels north and south than they do if we travel east and 

 west. The higher plants are unable to move about by their 

 own efforts, as animals do, but the young plants in the seeds 

 are usually provided with some means of locomotion by 

 which they spread into new regions. Many seeds have tufts 

 of hairs which serve as parachutes delaying their fall to the 

 ground and thus carrying them to new places, others have 

 winglike projections and are blown about by the wind, and 

 still others are covered with a juicy pulp which ensures their 

 being carried to new localities by birds and other animals. 



