Ecology of the Cincinnati Region 
201 
first year seedlings of Salix nigra and Popuhis deltoides. Here, although 
zone II (dg. 55^ contains many tree seedlings, the plants are all of the 
current season’s growth ( 1913 ). If these endure, and the banks are built 
out in front of them, a new and younger zone is initiated.® The causes 
Fig. 54. The same flood plain forest viewed from the shore. 
which permit the sudden appearance of this new zone have not yet been 
determined. It is probable, as willow and cotton-wood seeds will germi¬ 
nate only on moist ground, that a great deal depends on the stage of the 
river at the time of seed ripening. 
The second association of the flood plain formation consists most 
commonly of small willows and cotton-woods, but in many places other 
trees may enter in, among which are sycamore, white elm, box elder 
(Acer Negnndo), and silver maple (Acer saccharinuni). In the succes¬ 
sion shown in dg. 5^, this zone is made up of willows and poplars showing 
®yhe belt transect, fip. 55 , shows the conditions late in June, 1914, one year later. The new 
zone in this is called zone O, and the other zones numbered in accordance with the photographs 
