182 WIND-DISTRIBUTION OF SEEDS. [CH. XIV 



fall slowly through the air and may readily be carried 

 to some distance from the parent. A seed of this sort is 

 given in fig. 83. 



FIG. 83. 



SEED OF BIGNONIA ALBO-LUTEA, 

 showing the expanded membranous edge or wing. Life size. 



The fall of these seeds is beautiful to see ; they swoop 

 and shift with a zig-zag flight, like a rook or peewit 

 " tumbling " in the air, or like a slate falling through water. 



In some cases seeds which are not flattened, or winged 

 with membranous borders, are distributed by an arrange- 

 ment called the " censer mechanism." This may be seen 

 in the Larkspur (Delphinium) : the minute shining seeds 

 are found, when ripe, lying loose at the bottom of the 

 pod-like seed-capsules. They cannot fall out because the 

 capsule is closed except for a cleft near the top, but can 

 be jerked out by anything that shakes the plant, 

 probably the wind or a passing animal would serve the 

 purpose in a state of nature. The poppy scatters its 

 seeds by the same mechanism, the seed-capsule being 

 pierced by a ring of small holes just below the radiating 

 stigmas which crown the capsule. In these and similar 

 cases the fact that the seeds are not easily thrown out of 



