SEEDS AND FRUITS CARRIED BY ANIMALS 85 



Darwin took 3 tablespoonfuls of mud from beneath the water at 

 the edge of a pond and kept it in his study until the seeds con- 

 tained developed into plants. From this small amount of mud, 

 he obtained 537 plants which represented a number of species. 

 From this it is evident that the 

 mud, carried on the feet and legs 

 of water birds, may be the means 

 of distributing many seeds. 



The fruits and seeds of many 

 plants have spines or small hooks 

 by which they become attached 

 to passing animals and are carried 

 far and wide. Some familiar ex- 

 amples are the burs of Burdock, 

 Cockle Bur, and Sand Bur, and 

 the hooked and spiny fruits of the 

 Buttercups, Wild Carrot, Beggar's 

 Lice, Tick-trefoils, Beggar-ticks, 



and Spanish Needles. They catch 



_ J .. FIG. 87. A Chickadee carrying 



in the wool, manes, and tails of fmit From Bulletin ^ Iowa Geo . 



stock and in the clothing of man, logical Survey. 

 and are carried from one pasture 



to another or from one farm to another. Live stock are impor- 

 tant agents in distributing plants on the farm. The seeds of 

 the Mustards are mucilaginous when wet and, by sticking to the 

 feet of animals or the shoes of man, are carried to new situations. 

 (Fig. 88.) 



Many plants owe their distribution to man more than to any 

 other agent. The railways, connecting all of the states and 

 reaching from ocean to ocean where they connect with steamship 

 lines from across the seas, are responsible for the wide distribution 

 of many plants. For example, the seeds of a number of weeds 

 are shipped across the country with grain and other farm seeds, 

 and also in hay, bedding, packing, in shipments of fruit, and 

 in the coats of live stock. They fall from the cars as the train 

 travels, and seed the right-of-way where the plants first appear 

 and then later spread to the surrounding fields. The railways 

 are responsible for the wide distribution of Russian Thistle, 

 Prickly Lettuce, Canada Thistle, and Texas Nettle, which first 

 appear along the railway and later spread to the surrounding 



