FIELDBOOK OF ILLINOIS WILD FLOWERS 



fruit in question: though these differences seem trivial at times, 

 they are very important in referring the plant in question to its 

 appropriate family in its classification. They tell us whether 

 the fruit is the product of a flower cluster or a single flower, 

 whether it came from the ovary of a flower which was free from 

 the calyx or one which was united with the calyx, etc. 



DISSEMINATION 



Some fruits are disseminated while still containing their 

 seeds, which are shed from them later; other fruits shed their 

 seeds while still attached to the plant. 



Seed dispersal structures and agents of dissemination. — ^The 

 fruit of the elm and ash illustrate the samara, or "key fruit," 

 which has wings that readily provide dispersal by wind. Fruits 

 of the maple and box-elder are often double. 



Many seeds of the dehiscent fruits are provided with special 

 parts which facilitate their dissemination. The seeds of milk- 

 weeds and Cottonwood have tufts of long hairs, outgrowths 

 of the seed coats. Seeds of the catalpa tree are flat and fringed 

 on the margins so they are easily borne by the wind. Such 

 naked seeds outwardly resemble but are not true samaras, in 

 that true samaras are fruits containing seeds. When the fruits 

 of the touch-me-not, violets, the lupine and wild geranium split 

 open, the seeds are thrown out with such violence that they are 

 propelled through a considerable distance. Thus the variety 

 of methods by which fruits and seeds are disseminated is so 

 great that close observers may still hope to discover some special 

 method which has not been fully described in a textbook, and 

 many nature lovers derive great pleasure and satisfaction trom 

 the pursuit of their observations on seed dissemination. Some 

 naturalists make extensive collections illustrating the great 

 variety of methods of seed dispersal. 



Water is less common than wind as an agent of dissemination, 

 but is important in that it may carry fruits or seeds tor long 

 distances. Many seeds and fruits are lighter than water and 

 will float almost indefinitely, as, for example, seeds of the larger 

 blue flag; they are protected by a corky outer layer that water- 

 proofs them for a considerable time. Such seeds, however, at 

 length absorb water and sink, or continue to float but lose their 

 ability to germinate. Consequently, there is a limit to the dis- 

 tance and time they may be transported by water and still 



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