The Various Ways in Which Plants Appeal 13 



ations which often have more influence than adaptation itself. 

 Thus, in addition to the principal adaptation, (such for example 

 as the flatness of a leaf in adaptation to the need for spreading 

 much surface to the light), there are secondary adaptive needs, 

 such as for protection against dryness or other hostile influences. 

 Further, a prominent feature may not be adaptive, but incidental 

 to some other process, as in autumn coloration of foliage, or the 

 mathematically-arranged origins of leaves: or it may be merely 

 a mechanical effect, like the drooping of old branches of evergreen 

 trees: or it may represent an individual adjustment to one feature 

 of the surroundings, like the bent-over leaf-stalks of house plants 

 in windows : or it may be inherited from the past without present 

 significance, as in the compound early leaves of the Boston Ivy: 

 or it may represent a spontaneous new variation, or mutation, 

 or sport, such as originate new garden varieties of flowers, leaves, 

 or fruits; or it may have yet other meanings of minor sort. These 

 cases and illustrations will all be further explained in the following 

 pages, and I merely cite them to show that not all features of 

 plants are adaptations, while all adaptations are interwoven more 

 or less with these other considerations, the actual structure being 

 the resultant of the interaction of them all. The matter can be 

 expressed in this way, that adaptation can never fit a condition 

 as an old glove fits the hand, but rather as a cloak fits the body. 

 One should therefore neither expect too much of it on the one 

 hand, nor reject it altogether on the other. The real problem is 

 not so much to find adaptations as to separate out and define 

 the various factors that enter into the combinations of which 

 adaptation is only a part. 



One other important phase of the relations existing between the 

 human mind and the workings of organic nature, concerns the 

 question as to whether there is anything in living beings except 

 physics and chemistry, in other words whether they are mechan- 

 ism only, or whether the mechanism is inspired by vitalism. The 

 evidence seems to be showing clearly enough that all of the in- 



