630 



WEED FLORA OF IOWA 



Fig. 493A Fig. 493B Fig. 4930 



Fig. 493. A. Seed of common Field Sorrel (Oxalis corniculata) with two cap- 

 sules from which the seeds are shot out. B and C. Common Dock (Rumex 

 crisj)us). Fruit scattered by the water. The wings surrounding the fruit and 

 tubercle make the fruit admirably adapted to floating on the water. Sec- 

 tion of the fruit showing wings and tubercle shown in C. 

 (Drawings by Ada Hayden.) 



Parts of the fruit which serve as disseminating mechanisms. — ■ 

 The stimulus of fertilization not only gives rise to the development 

 of a seed but causes parts of the seed or seed-case to develop in 

 many instances into a special contrivance for its dissemination. A 

 fruit, botanically speaking, is a ripened ovary, including any 

 closely attached parts, for example: the milkweed pod filled with 

 seeds bearing tufts of hairs ; the dandelion fruit with its parachute- 

 like pappus. 



Parts which serve as dissemination mechanisms: 

 Ovary wall. 



a. Fleshy, often attractively colored — cherry, horse 

 nettle, black nightshade. 

 Bursting — touch-me-not. 

 Inflated — sedge. 

 Corky tubercles — dock. 

 Winged — maple. 



b: 

 c. 

 d. 

 e. 



Calyx, 

 a. 

 b. 



Capillary hairs — dandelion. 

 Spined — buffalo bur. 



