ak6 BOTANICAL GAZETTE focropeR 
and four bracing extensions running downward and away from the 
track, nearly to the base of the high grade (jig. 1). The riprap wall, 
running parallel to the roadbed and 1.2™ below it, is 60™ long, 
varies from 1.5 to 2.5™ in perpendicular height, and rises at an angle 
of 45 to 55°. The four bracing extensions run down the sides of the 
grade at right angles with the wall above and at an angle of about 30°. 
The length of the extensions averages about 21™, and they vary from 
2 to 2.7" in width. A grass-sedge swamp lies to the north of the 
and portions of two of 
nd the general plan of 
Fic. 1.—View of a portion of the northward-exposed wall 
the extensions, showing something of the spermatophytic flora a 
structure of the ripra 
t seasons 
bout 12”; 
k bed, 
built 
society and contains a considerable amount of water in we 
The vertical height of the grade above the swamp level is a 
and the riprap extensions pass from within 1.2™ of the trac 
downward to within 3™ of the swamp level. The riprap Was 
in 1874 and is thus thirty years old. 
II. ECOLOGIC FACTORS. : SS 
The conditions as a lichen-bearing substratum are ee pe 
number of ways. Though the same rocks used for gee 
buildings and ten or more years older are apparently sound, the 
