TILE DRAINAGE. 35 



cept of water-growing or swamp-crowing trees, willows, 

 wliite elms, etc.) must iiave nir as well as moisture, as was 

 fully explained in Chapter II. When the proper air-spaces in 

 the soil are soaked full of water, the roots suffocate, so to 

 speak, or drown, like land animals held too long under water. 

 And as such animals struggle and swim to the surface to get 

 air, so do the roots run close to or even half upon the sur- 

 face, to </<'/ 0-ir. Notice the roots, especially of sugar maples 

 and apple-trees, if you have a chance. In my own " sugar- 

 cam] v 1 part of the maples grow along a brook-valley on soil 

 rather gravelly and naturally drained. These trees strike 

 their roots down deep, and are very thrifty and strong. But 

 a part, of the trees are on wet, cold, level, upland-clay soil. 

 Here the roots run for rods near and even on the surface. I 

 used to think it was because the soil was so thin, and the 

 subsoil so hard and impervious; but upon further study I 

 am convinced that it is because it is too wet. The roots are 

 swimming on the surface v to get a chance to breathe ! 



The same is true in this apple-orchard. In plat 2 of Fig. 8 

 (compare Fig. 10). the roots grow so close to the surface, that, 

 even while the trees were comparatively small, a few years 

 of cultivation cut and broke many of their roots, and the 

 trees died, partly from that cause and partly from overwet- 

 ness in wet times, and the hard lumpy condition of the soil 

 in dry times. 



But in plat 1 (compare Fig. 9) the roots struck down deep 

 into a soil aerated and rendered more mellow by tile drain- 

 age, and found'sufticient moisture the whole year round, but 

 never excessive, and were helped and not damaged by the 

 tillage of hoed crops growing among them. 



EXACT STATISTICS OF MORTALITY. 



Fig. 8 gives the means of ascertaining these. As stated, 

 the mark + shows just where each original tree (or tree re- 

 placed before the land was tiled) remains alive and thrifty, 

 and the mark O shows each place where one has died and 



