260 NICHOLS: THE VEGETATION OF CONNECTICUT 
For while, like the willow, the cottonwood is relatively intolerant 
of shade, it grows more rapidly and to a much larger size, so that 
it tends to overtop and shade out the willow. Meanwhile other 
trees make their appearance. In’ addition to the species already 
enumerated, common trees on the Connecticut River flood plains 
are the elm (Ulmus americana), silver maple (Acer saccharinum), 
basswood (Tilia americana), white ash (Fraxinus americana) and red 
ash (Fraxinus pennsylvanica). Without exception, all of these last- 
named trees are more tolerant of shade than their predecessors. 
Springing up in the light shade which the cottonwood and willow 
produce, these more tolerant species become increasingly abundant 
until ultimately they dominate the forest. And while today the 
cottonwood and willow are perhaps the most conspicuous trees 
of the Connecticut River flood plains, there is little doubt that the 
forests which originally clothed the higher flood plains were made 
up largely of elm, silver maple, basswood, and ash. 
A striking feature of the vegetation in flood plain forests 1s 
the wealth of lianas. Woody forms, such as Rhus Toxicodendron, 
Vitis vulpina, and Psedera quinquefolia, ascend the trunks of 
trees and hang in graceful festoons from the branches. A few 
herbaceous lianas also, notably Sicyos angulatus and Echinocystis 
lobata, clamber the trees, while numerous less vigorous species, ¢-8- 
Polygonum scandens, Amphicarpa monoica, Convolvulus sepium, 
‘Solanum Dulcamara, and Clematis virginiana, twine about or cling 
to any available support. The parasitic Cuscuta obtusiflora is @ 
common form on the Windsor flood plain. Shrubs are usually few 
and scattered, about the only forms ordinarily present being Cornus 
Amomum and Sambucus canadensis. 
The herbaceous undergrowth in such a forest is rank and 
luxuriant; some idea of its character is conveyed by FIG. 10. 
Tall, broad-, thin-leaved mesophytic plants predominate. The 
giant ragweed (Ambrosia trifida) commonly reaches a height of 
from ten to twelve feet, and the ostrich fern (Onoclea Struthiopteris), 
largest of the native ferns, a height of more than six feet. € 
nettles (Laportea canadensis and species of Urtica), growing more 
than waist-high, are uncomfortably abundant. ‘Other charac 
teristic herbaceous species worthy of mention are the follow- 
ing: 
