42 2 Minnesota Plant Life. 



gale along" the lee shore of some Minnesota lake, one may see 

 the bulrush stems beaten into the water by the wind and surf, 

 only to rise again erect and unharmetl when the waves are 

 calm. Such elasticity is procured by special structural areas 

 in the stem, disposed in highly accurate fashion so as to take 

 up the lateral strains evenly and effectively. The cross-section 

 of a bulrush stem shows it to be as cunningly constructed as the 

 finest bridge-truss, with girders, flanged in the regulation style. 

 made up of the so-called "tension ])ieces" and "compression 

 pieces" of the architect, and constituting an altogether admi- 

 ral)le piece of structural engineering. Such contrivances are 

 not needed b}' ])lants growing under other conditions and will 

 not be found. Elasticity, for example, is not a noteworthy char- 

 acteristic of the stem of submerged a(|uatic ])]ants li\ing in 

 cjuiet pools; but if the stem grows in running water it is some- 

 times more elastic. Roots, in general, being underground in 

 their habit, are not so much exposed to occasional displacing 

 forces as are stems and, therefore, are by no means so elastic. 

 It is easy to compare, in these regards, a grass stem and a grass 

 root. If the living erect stem of a rye plant is bent down it 

 Cjuickly resumes its original position ; but if the root is bent to 

 one side the resumption is but slight, or there is no resilience. 



In certain parts of the world, where heavy falls of snow occur, 

 a weight is in this way piled upon the branch system, and the 

 ])lant |)erlia])s responds to such a climatic state l)y growing in 

 the f(jrm of a tkit, prostrate shrub, as many of the heaths have 

 done. ( )r. if it be a tree, it learns to produce strong drooping 

 lateral branches like those of the spruces. When grown in a 

 lawn, these trees retain the droop of their branches or branch- 

 lets — originall}- a structural device for shedding masses of snow, 

 that might otherwise break the branches by their weight. 



Plants that j^roduce abundant and hea\\- fruits nuist, if they 

 sui)port the weight of these fruits, dexclop strong branch sys- 

 tems, or otherwise llie body of the ])lant will be broken. Of 

 this the apple trees of orchards furni>li good examples. The 

 branches of the a])])le are ])ullcd into a more horizontal posi- 

 tion by the increasing weight of the fruit and many of them 

 actually droop. The main branches will. howe\er, be found to 

 be strong and well buttressed against the trunk. \'ery often, 



