10 AMERICAN JOURNAL OF BOTANY [Vol. 9 
(Michx.) Torr., and Panicum sp. ; further, Liatris squarrosa Willd., L. scariosa 
Willd., Petalostemum purpureum (Vent.) Rydb., Euphorbia corollata L., 
Croton monanthogynus Michx., Astragalus mexicanus A. DC, and especially 
TrifoUum stoloniferum Muhl. and Plantago aristata Michx. predominate; 
like the true prairies, these barren places have no vernal flora. 
This description of the plant societies and associations of the Ozark 
uplift of the southeastern portion of Missouri gives a general idea of the 
nature of its flora. 
The lowlands, covering about 7,500 square kilometers and lying about 
300 feet above sea level, are largely composed of residue from the Mississippi 
River and its tributaries, such as the Black River, St. Francois River, 
and others. These bottom lands are composed of various types of very 
fertile loam soils. They are complex in origin, as the various rivers obtained 
their material from such sources as the residual uplands, the plains, the 
loessial and glacial prairies; consequently they difl^er from one another in 
composition and color, ranging from sandy loam to silty loam. The soils 
west of Crowley's Ridge, representing the old valley of the Mississipp 
River, are very old; usually they are grey in color; through poor drainage 
and constant leaching a considerable loss of lime, iron, and sometimes of 
phosphorus has resulted. A silty loam of a great depth is the principal 
soil of this region ; it includes most of the land between the upland and the 
western part of Crowley's Ridge. The northern part, however, consists of 
recent alluvium, derived from the uplands, and contains at various places 
much organic matter. The subsoil usually is a drab silty clay. 
West of Crowley's Ridge, in Stoddard County and Ripley County, a 
relatively large area is found with fine sandy loam; it is greyish brown to 
yellowish grey, whereas the subsoil is composed of sandy clay; it contains 
many iron concretions, which may result in hardpan formation. This 
country stands three to eight decimeters above the surrounding lowlands. 
From about Cape Girardeau County throughout the lowlands toward 
the boundaries of Arkansas, the soil is heavy and contains much organic 
matter, whereas the subsoil is of a close structure. These areas are the 
lowest of any part of southeastern Missouri, which fact has resulted in the 
formation of swamps of considerable extent. 
These swamps are of extreme interest to the ecologist ; many formations 
and associations are here to be encountered, starting in the floating plant 
associations of Lemnas and ending in the strange swamps with Taxodium 
and monotonous Nyssa forests. 
Following the various facies of the different plant associations, one may 
readily distinguish the stagnant pools and ponds, the surface of the water 
thickly covered by floating plants most of which belong to the Lemnaceae; 
a pond is covered either by a single species or by several. The following 
are found: Wolffia punctata Griseb., W. papulifera C. H. Thomps. (rare), 
Wolffiella floridana (J. D. Sm.) Thomps., Spirodela polyrhyza (L.) Schleid., 
Lemna valdiviana Phil., L. perpusilla Torr., and L. minor L. Azolla caro- 
