THE PROBABLE ORIGIN OF KEY-FRUITS. 235 



producing a minute winglike appendage on the end or margin, as 

 is in reality the case with the fruits of many plants. Violent 

 winds, such as sweep perennially over such regions, carry a few 

 of the nascent key-fruits out of the ravine where the parent-tree 

 grows, and perhaps, after being borne through the air for a con- 

 siderable distance, a few fall upon the fertile and unexhausted 

 soil of another draw, or flood-plain, which is as yet unpeopled by 

 trees. The unappendaged seed-vessels, unable to fly far with the 

 winds, perish in the tree-crowded coulee or upon the barren hills. 

 Plants that spring from the seeds of such fruits, by virtue of the 

 laws of inheritance, will themselves have a tendency to bear 

 fruits lacking the incipient wing, and growing as they do in im- 

 poverished soil, will stand but an unfavorable chance in life, as 

 will their descendants also. Likewise, the trees that spring from 

 the seeds of appendaged fruits by heredity will tend to produce 

 this kind of seed-vessels themselves. Thus year in, year out, the 

 selection and elimination goes on, and it can easily be understood 

 how, in time, first a samaroid and later a fully-winged fruit will 

 be evolved. Sometimes among hundreds of perfect ones we find 

 a maple key- fruit the wing of which is very short and rounded; 

 that is, has been arrested in its growth. Such partly-developed 

 samaras illustrate an early stage attained ages ago in the evolu- 

 tion of the typical specimens. 



Without a wing of some sort, countless thousands of the 

 fruits would annually be stranded amid the unproductive hills, 

 and even as it is I have often found samaras of ash-trees and 

 box-elders inextricably entangled in dense mats of buffalo-grass. 



To support the idea that the ancestral trees may have been 

 driven to develop this peculiar form of seed-vessel in order that 

 seeds might be carried from one productive spot, in an arid or 

 semi-arid country to another, I may adduce the fact that plants 

 indigenous to desert regions often have special means of insuring 

 the transportation of their seeds across the barren wastes, to moist 

 and fertile tracts. Says Lubbock, " The Anastatica hierochnntia, 

 or * Rose of Jericho,' a small annual with rounded pods, which 

 frecjuents sandy places in Egypt, Syria and Arabia, when dry curls 

 itself up into a ball or round cushion, and is thus driven about by 



