THE AMERICAN BOTANIST. 91 



in straight lines or rows. Those nearest the parent plant are 

 of course the oldest and have the advantage in size, while the 

 younger are all successively smaller. This habit of growth in 

 lines is shown by many plants, but seldom so regularly or so 

 conspiculously as by this rush. 



What boy or girl has not thrown maple seeds into the air, 

 and watched them whirl rapidly as they slowly fell to the 

 ground? Many other plants have fruits or seeds which be- 

 have in the same way, and some of them can be found almost 

 any time during the summer. Ash, linden, box elder, and 

 tree-of-heaven are some common examples. W'hy do they 

 whirl so? Try some of them, examine them carefully, and see 

 if you can find out. If you have studied physics, compare the 

 motion of the seeds with what you have learned about the in- 

 clined plane. As to the use of it. one can easily see that by 

 falling so slowly they can be carried farther by the wind be- 

 fore they reach the ground. 



Sometimes our wild plants have difHculties in getting their 

 seeds properly planted. A curious incident of the accidental 

 planting of seeds was observ^ed this summer on an area of bare 

 sand. Every year the wind blows thousands of seeds upon 

 this sand, but the next wind will blow many away, and those 

 that remain have no means of getting down beneath the surface 

 to a depth suitable for germination. A wagon had been driven 

 across this sand just at the right season. The heavy wheels 

 had crushed the seeds down two or three inches into the sand 

 so that in the spring they had a favorable opportunity to grow^ 

 As a result, the route of the w'agon is marked by rows of living 

 green plants, indicating the position of every wheel track, while 

 elsewhere the sand is almost bare. Many of the plants in these 

 rows are Partridge-pea, which has very showy yellow flowers, 

 so that the wheel tracks at this season are outlined in yellow 

 and visible from a long distance. 



