1910] HOWE—REFORESTATION OF SAND PLAINS 137 
trichum appear in the most sterile places. Driving out the biennial 
and perennial weeds, the groups unite and form patches of moss a 
meter or more in diameter. The moss in turn may be crowded 
out by Cyperus and Danthonia, but it is never entirely displaced. 
Patches of Polytrichum often occupy one-third of the area in old 
fields. 
Some of the plowed fields were abandoned because they began to 
blow away, and they have since become areas of shifting sand. This 
is notably the case in several places in the townships of Colchester 
and South Burlington. The finest sand is piled up in low dunes and 
the coarser grades left behind are packed hard by the wind. Cyperus 
jiliculmis and Panicum sanguinale are the pioneers on the compact 
sand; the former occurs in groups, while the latter advances en masse 
upon the sand. The open spaces between the groups of Cyperus are 
filled up by Polytrichum. 
The patches of Polytrichum in the abandoned fields described 
above form ideal germinating beds for the seeds of pitch pine, white 
pine, and white birch. This is particularly the case when the Poly- 
trichum is young, before the dead leaves and stems have accumulated 
sufficiently to prevent the seeds from reaching the mineral soil. 
Usually, however, Myrica precedes the tree invasion. It starts in the 
bed of Polytrichum and itself forms patches, killing out the moss 
immediately beneath it. The Polytrichum, however, persists around 
the margins of the Myrica group and in the moss, and under the 
protection of the Myrica one finds the tree seedlings. 
The rapidity with which trees take possession of the abandoned 
fields of this type chiefly depends upon the proximity of seed trees. 
Thus a field 370™ from seed trees, abandoned 20 years ago, has only 
41 white birch and 6 pitch pine saplings per hectare. When the pines 
get old enough to produce seed, a group of young trees will be formed 
about each mother tree. Fields showing two generations of pitch 
pine formed in this manner are of common occurrence and those 
showing three generations are not rare. The white birch, being 
shorter lived and less tolerant than the pine, is gradually suppressed, 
and the result is a pure stand of pitch pine of uneven age. A list 
chart in the field mentioned above shows on one square meter 16 
Solidago memoralis, 24 Carex pennsylvanica, 18 Lysimachia quadri- 
