196 BOTANICAL GAZETTE [MARCH 
forests that usually border them. It is obvious that trees do not 
grow in them because the amount of moisture in the soil is too great. 
Some of the meadows have been artificially drained, others have 
been planted to timothy, and one in particular, in the northwestern 
corner of the area (map), has been drained and cultivated for a num- 
ber of years, so that its former nature was discovered with difficulty. 
What has been done artificially is being done naturally, but more 
slowly. The detritus that is washed into the ponds and the vegeta- 
tion that dies down from year to year are filling up these bodies of 
water, and are making the meadow condition possible. Again, the 
streams are cutting their channels deeper, thus lowering the under- 
ground water level at their borders, and this changes conditions that 
favor meadows and introduces those that make the forest possible. 
It is very probable that many areas now occupied by spruce and other 
forests were formerly occupied by meadows. Indeed, all stages of 
development towards this forest condition were noted, and will be 
discussed under the next head. 
THE SPRUCE FORMATIONS (MESO-HYDROPHYTIC). 
In many places species of Salix and Alnus incana encroach upon 
the meadows, sometimes forming dense breastworks around the 
grass areas, so that it is difficult for other trees to get a start. This 
is the case when the zones of underground water level are sharply 
and narrowly marked off. Usually, however, when the underground 
water level is at a fairly uniform distance below the surface for 4 
rather broad area, as it is where the small streams spread out over @ 
level extent of land, the willow-alder breastwork is absent. These 
situations are favorable for the advance of Picea Engelmanni into 
the meadows. The youngest trees are found on the hummocks 10 
the meadows; nearer its’ borders are the older ones, though they 
are still scattered; these grade imperceptibly sometimes into dense 
forests of spruce, many of the trees reaching huge dimensions. since 
this formation is found best developed on situations where the under- 
ground water level is a little farther below the surface than it 5 
the meadows, it may be called the meso-hydrophytic formation. 
It must not be supposed that there are no other trees with the 
spruce; indeed there are only small tracts where pure spruce woods 
