THE EVOLUTION AND VARIATION OF FRUIT PLANTS. 25 



fructified germ, because a changed mode of nutrition has destroyed 

 the capability of reproduction. Varieties of all species of fruit will 

 deviate frequently in important peculiarities, as a consequence of 

 different conditions of nutrition, air, and light. But there is a 

 limit to the adaptability of every organism, for in aged fruit trees 

 only the most necessary organs of nutrition and propagation 

 retain their activity ; the remainder have degenerated ; a diver- 

 gence in a retrograde direction has taken place, which is a 

 relapse to simpler conditions of life. 



Few wild fruits become extinct, and many are of sufficient 

 value to be worthy of improvement by cultivation. In their 

 native haunts their quality is improved by pure air, rich soil, and 

 bright sunlight. But the}' often change their conditions. Wild 

 strawberries will disappear in the meadows, but reappear again in 

 after years. A piece of forest land burnt over and left uncleaned 

 will frequently be occupied by red raspberries ; after a short 

 period by black-caps and later by blackberries ; all of which 

 disappear in time and give place to other plants. Adventive 

 species are also sometimes found which have strayed from domestic 

 care. They appear and vanish because they cannot long endure 

 the conditions of climate, but a change in their habits is fre- 

 quently brought about by artificial methods of propagation. 

 There are no signs among Nature's laws that indicate a tendency 

 to the dying out of our favorite fruits ; neither do they fail from 

 necessity or in accordance with irrevocable laws. To explain 

 fruit deterioration we must not look to causes inherent in the 

 variety, for when we speak of degeneration of fruits or a decline 

 in their good qualities, we mean that certain varieties do not 

 maintain their character for healthfulness, hardiness, and produc- 

 tiveness ; and this lack of vitality may be due to enervating 

 methods of growing, the mutations of seasons or climatic influen- 

 ces, incessant propagation from the same stock or perpetual 

 growth upon the same spot, and to the mildews, rusts, rots, and 

 other fungous elements which are of recent origin, all implying 

 degeneration of culture but not of varieties. Fruits demand 

 constant care and high cultivation to keep them up to the standard, 

 and Nature permits no deterioration unless she is interfered with. 

 We think we raise the standard, but it is an artificial one and 

 must be maintained by artificial care, lacking which Nature goes 

 back to her original criterion. 



