THE RELATIVE HARDINESS OF PLANTS. 797 



nally. The use of the stick or stone in defense set in motion a new 

 process of adaptation which has tended toward a physical weakness, 

 at least in regard to conflict with wild animals. 



It was, in fact, the first step in the enhancement of animal force by 

 the employment of the vast stores of inorganic force existing through- 

 out nature. It was the earliest inventive action, the bringing of outer 

 nature to human aid, which has since produced such wonderful results. 

 Muscular vigor and acuteness of sense have probably decreased as they 

 have been thus partly replaced. For man has gained new muscles, in 

 his use of the forms and forces of the inorganic world, and has com- 

 menced a new process of adaptation, which has already enabled him 

 to extend his kingdom from the tropic to the frigid zone, and which 

 promises to make him to some extent master of the fields of water 

 and air. And his mental exjierience of wider and wider conditions of 

 nature has produced a new form of physical adaptation that signi- 

 fied in clothing and habitation. 



But this opens a new subject, too wide to be considered here. We 

 can only end as we began, with the assertion that the human form oc- 

 cupies the apex of possible organic development, and forms the true 

 foundation for that higher mental evolution which is still growing, 

 branching, and flowering upward. 



---- 



THE EELATIYE HAEDINESS OF PLANTS. 



Br SAMUEL PAESONS, Jr. 



THE isothermal line, curving up and down the map, is no inapt 

 illustration of the course another line would take on the chart 

 which sought to explain the relative hardiness of plants, only the curves 

 of the latter would be more complex than those of the former. Who, 

 indeed, could direct aright such a line for even individual species ? 

 and for varieties it would be wellnigh impossible. Scarcely could re- 

 liable data be furnished for the broader division of genera. And yet 

 the investigation that does not take into account varieties misses a large 

 number of plants possessed of the most noteworthy and valuable in- 

 dividual traits. The question may be easily asked, Wherein lies the 

 difference between a variety and a species ? but the answer evidently 

 is not so easy, when we consider that every individual plant varies in 

 a degree from all other plants ; and, to render it still more diflicult, we 

 find botanists very properly ignoring the existence of varieties that 

 may have individual characteristics invaluable to the planter. 



Latitude, moreover, we find is only one factor, and a very vague 

 one, in the problem of determining the relative hardiness of plants. 

 Climate is the real governing. element climate, that vai'ies with the 



