
1901] GENETIC DEVELOPMENT OF FORESTS 297 
THE MIDDLE BEACH. The middle beach is that portion of 
the shore drift in transit only during the winter months. It is 
consequently free from the waves during the growing season. 
Here, therefore, is a new land formation in which all the factors 
which prevent growth in the lower beach are eliminated for the 
brief space of one growing season. While the hydrodynamic 
factors have been eliminated, certain of the atmospheric, edaphic, 
and historical factors are detrimental. Since the former are 
considered in the initial stages of the upper beach society, they 
will be discussed under that head. In the short period that this 
beach is left untouched by the wave action, no plants of any 
consequence can obtain a foothold. This, together with the 
sterile soil of sand or pebbles and the extreme exposure to 
insolation, often prevents the growth of any species. In a few 
instances the annuals, Cakile Americana and Corispermum hyssopt- 
folium, and the first year’s growth of the biennial, Oenothera 
biennis, are present. If the new land thus made contained an 
alluvial soil stocked with seeds, one might expect a more or less 
abundant growth of annuals, though the insolation would still 
be very great, and would undoubtedly prevent a rich growth. 
Since the middle beach, by a further recession of the waters of 
the lake, may become a fossil beach, and thus reach, as will be 
shown later, a condition more near the forest, it is regarded as 
the second stage in the life history of the forest. 
FossiL BEACH. The fossil beach is that portion of the shore 
beyond the reach of the hydrodynamic factors. In the initial 
stages the fossil beach is as barren of vegetation as the middle 
beach, and if in an exposed situation the wind (fig. 1) shifts 
the sand repeatedly, this condition is maintained for a greater 
or less length of time. If fairly well protected from winds, 
successive plant societies appear rather rapidly. 
The well-known physical and chemical qualities of sandy soils 
need not be discussed at length here. While the upper layers 
of sand dry out rapidly, observations seem to show that the 
lower layers are moist up to high levels. However, the first few 
layers are extremely dry after a short period of drouth, due to 
