DISPERSAL OF WEED SEEDS 15 



II. WATER. 



A. Seed with light, inflated pods, Sedges. 



B. In large receptacles, Nelumbo (Water Chinquapin). 



C. Mucilaginous seeds, Pepper Grass. 



D. Currents of water in a mechanical way, Driftwood. 



E. Plants floating on water because provided with air spaces, 



Lemna (Duckweed). 



III. SNOW AND WIND COMBINED. 



Many weed seeds. 



IV. ANIMALS. 



A. Fleshy, edible fruits and seeds, Nightshade, Cherry 



B. Edible seeds not fleshy, Sunflower, Acorn. 



C. Fruits with hooks or barbs, Bidens (Beggar-ticks). 



D. Seed or fruits with webs, Blue Grass. 



Fig. 6. A tumble weed, winged pigweed (Cycloloma atriplici- 

 folium), scattered by its tumble habit. The Russian thistle and a kind 

 of pigweed are scattered in the same way. (U. S. Dept. Agrl.) 



V. EXPLOSIVE PROPERTIES OF FRUITS AND SEEDS. 



A. Contraction of seed vessel, as in Hura crepitans 



B. Twisting of pod, Vetch. 



C. Tension in pod, Impatiens (Jewel-weed). 



D. Shooting of seeds, Oxalis. 



E. Turgidity of fruit, Squirting Cucumber. 



VI. CREEPING MECHANISMS AND BY THE SEEDS BURYING THEMSELVES. 



A. Hygroscopic movements, Stipa. 



B. Cleistogamous flowers, Violet. 



VII. MAN AS AN AGENT. 



A. Impure seed, Clover Dodder. 



