1995] TRANSEAU—BOGS OF THE HURON RIVER VALLEY 423 
principal seat of root activity. The small, fibrous roots of cassandra, 
andromeda, and the cranberry penetrate it in all directions, and it is 
from the water which is held among this moss and débris that they 
derive their water and mineral salts. 
The substratum beneath the tamaracks is also covered by a loose 
litter of leaves and twigs, with more or less moss. Depending upon 
the height above the ground water level, this surface layer is of greater 
or less thickness. In it occur the wide-spreading roots of the tama- 
rack. During summer and autumn it furnishes admirable conditions 
for the growth of fungi, and it is penetrated everywhere by their 
mycelia. 
When bog land is cleared, the decomposition of the surface layers 
is very rapid, owing to exposure to sunlight and higher temperatures. 
If the water-table is maintained near the surface, sedges and willows 
develop as the covering. The annual increment of plant material 
is often decreased, and in place of the fibrous and porous substratum 
there is produced a black, close-textured, and plastic muck. 
If ditching and draining are added to clearing, the summer drought 
dries the surface layer so thoroughly that it often becomes the habitat 
for many dry-ground weeds. Decay progresses in moist weather 
under the influences of the higher temperatures resulting from 
increased absorption of the sun’s energy by the dark colored. soil. 
4. Mechanical properties—Bog soils in general de pat aliard ze 
good a foothold for the development of tree species as do the mineral 
Soils. On account of the high water-table, the roots of. the -plants 
are not able to penetrate to a depth of more than a few inches. The 
Toots of the tamaracks spread out in all directions from a flat trunk 
base, and upon the size and strength of these horizontal roots depends 
the tree’s ability to withstand mechanical strains tending to displace 
it. There can be no doubt but that, in the thick groves in which the 
tamarack occurs, the interweaving.of the roots from adjacent an 
becomes of mutual advantage, in so far as the roots function as hold- 
fast organs. 
5- Diffusion properties —A most important soil: property jsees 
to the diffusion of mineral salts. This becomes of especial al 
‘ance in saturated stagnant substrata. The mineral salts must 
distributed to the roots mainly by diffusion, for lateral, drainage 
