EXERCISE 53 



WHAT ADVANTAGES ARE POSSESSED BY PLANTS HAVING 

 WINGED SEEDS OR FRUITS? 



Materials. Winged seeds or fruits. Those of the maple, tree-of- 

 heaven (ailanthus), hop tree, box elder, and trumpet creeper are 

 good. Secure as many kinds as possible. 



Directions for work. Study the form and structure of the 

 wing and its effect upon dispersal of seeds. 



1. Action of wing. In the quiet air of the room drop several 

 seed's from as great a height as you can reach, and watch them 

 descend. Do they " fly away " ? That is, do the wings cause the 

 seeds to travel to distant parts of the room, or do the seeds alight 

 on the floor at a point almost directly below the point from 

 which they started? If the seeds descend directly, instead of 

 flying away, what is the effect of the wings upon the movement 

 of the seeds. 



Estimate the effect of the wings in the following manner. 

 Experiment with the seeds until you have found at least a 

 half dozen that descend at approximately the same speed. Then 

 remove the wings from one half of the seeds in the lot. Time the 

 fall of seeds with and without wings, as suggested below: 



Let one of the pupils ascend a step ladder or stand on a 

 table so as to be able to drop the seeds from a point near the 

 ceiling. Both the wingless seeds and the perfect ones should 

 be placed on the palm of the open hand, and all can be dropped 

 simultaneously by turning the hand palm downward. Let 

 another pupil count aloud at about the rate of a clock's ticking. 

 This can be best arranged by having a small clock in the room 

 and actually counting the ticks. Let one pupil begin counting 

 clock ticks while the other drops the seeds at a prearranged 

 signal, as, for example, the fifth count. The remainder of the 

 pupils should note the count at which the seeds start, the count at 

 which the wingless seeds reach the floor, and the count at which 

 the uninjured seeds reach the floor. Which lot of seeds descends 

 more slowly ? How much more slowly ? What is the real effect 

 of the wing ? Is the wing of any advantage, so far as dispersal 



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