HOW PLANTS ARE SCATTERED 379 
even after that (Fig. 269), often traveling for many miles 
before they come to a stop, and rattling out seeds as they 
go. Some of the commonest tumbleweeds are the Russian 
thistle (Fig. 268), the pigweed (Amarantus albus, Fig. 269), 
the tickle-grass (Fig. 270), and a familiar pepper-grass 
(Lepidium). In order to make a successful tumbleweed, a 
plant must be pretty nearly globular in form when fully 
grown and dried, must be tough and light, must break off 
near the ground, and drop its seeds only a few at a time 
as it travels. A single plant 
of Russian thistle is some- 
times as much as three feet 
high and six feet in diameter 
and carries not less than two 
hundred thousand seeds. 
449. Many-Seeded Pods 
with Small Openings. — 
There are many fruits which 
act somewhat like pepper- 
boxes. The capsule of the 
poppy is a good instance of 
this kind, and the fruit of 
lily, monkshood (Fig. 168), 
columbine, larkspur, and 
jimson weed (Fig. 271) acts 
in much the same way. 
Clamping the dry peduncle 
of any one of these ripe 
fruits, so as to hold it up- 
right above the table-top, and then swinging it back and 
forth, will readily show its efficiency in seed dispersal. 
Fig. 268. — Russian Thistle. 
