These often form floating or stable mats supported by a peaty mass of partly 

 decomposed plants. The outer edge of the bog has various types of tree species, 

 determined by that part of the world in which the bog lies. 



In small lakes in eastern and southeastern Texas floating mats are occasionally 

 formed where Decodon borders the water. Sedges, rushes, various species of 

 Hypericum and other such plants commonly grow upon these floating or quaking, 

 somewhat stabilized mats. Various evergreen or semievergreen shrubs and small 

 trees often border these lakes, among which are yaupon {Ilex vomitoria) , bay-gall 

 bush (I.coriacea), leatherwood {Cyrilla racemiflora) and viburnums. 



In most bogs, especially at great depths, there is little oxygen and, along with 

 acids formed by peats, decay is slow and fallen plants deposited in them often 

 only partly decay to become more peat. Because of their stagnant, usually highly 

 acidic environment, most bogs have their own peculiar flora, usually dominated by 

 thick-leaved shrubs and herbs. 



Two distinctive types of habitats, the evergreen shrub bog and savannah, occur 

 to a limited extent in our area. The savannahs are found only in southeastern 

 Texas and the bogs in southeastern and to some extent in eastern Texas. 



In pockets throughout eastern and southeastern Texas are found not only ever- 

 green shrub bogs but also open seepage slopes and cypress-tupelo swamps. The 

 latter also occur in southeastern Oklahoma. These usually develop in sandy, 

 seepy areas, either on or at the bottom of slopes, in scrub oak-pinelands, or in 

 permanently wet depressions in savannahs. They are characterized by usually 

 having peat moss (Sphagnum) present in varying degrees. The shrubs in and 

 about these habitats are often evergreen or semievergreen. They consist mostly 

 of viburnums, hollies, rhododendrons, bay laurel (Magnolia virginiana), wax- 

 myrtles, hypericums, dogwoods, vacciniums, leatherwood (Cyrilla racemiflora), 

 Lyonia, Itea, and occasionally a sprinkling of poison sumac (Rhus vernix). Often 

 the herbaceous vegetation is quite different from that of the surrounding country, 

 and is represented by such uncommon species as nodding-nixie (Apteria aphylla), 

 Bartonia texana, Viola lanceolata, grass-of-Parnassus (Parnassia asarifoUa), 

 bogmoss (Mayaca Aubletii), pitcher plant (Sarracenia alata) , rose pogonia 

 (Pogonia ophioglossoides) , bearded grass-pink (Calopogon barbatus), small wood 

 orchid (Habenaria clavellata) and yellow fringed orchid (H. ciliaris) . 



In extreme southeastern Texas, centered in Jasper, Tyler and Newton counties, 

 are savannahs of broad, level, grassy, open pinelands. These are characterized by 

 a fluctuating water-table, often found at or near the surface, and they support 

 a rather distinctive and interesting marshy and wetland flora. This includes 

 several orchids, as the snowy orchid (Habenaria nivea), crested fringed orchid 

 (H. cristata), grass-pink (Calopogon pulchellus) and several species of ladies' 

 tresses (Spiranthes) , yellow stargrass (Aletris aurea), pipeworts (Eriocaulon) , 

 whitehead bog-button (Lachnocaulon anceps), several meadow beauties (Rhexia), 

 clubmosses (Lycopodium) , milkworts (Polygala), small butterwort (Pinguicula 

 pumila) , bluehearts (Buchnera), sundews (Drosera), seedboxes (Ludwigia) and 

 numerous sedges, grasses and bulrushes that are indigenous to this type of com- 

 munity. The savannahs and shrub bogs, where they occur in proximity, commonly 

 grade into one another. Plants in this border-zone are often a mixture of those in 

 the two communities. 



The swamp, a wetland covered with trees and shrubs, is usually developed 

 from a marsh. Typically wet and occasionally flooded, swamp forests often 

 persist for a long time, especially when they are associated with streams that 

 periodically overflow. 



Originally an effort was made to coordinate pH and water temperature with 

 the exact place of growth for a species, such as those of Potamogeton, but it was 

 soon realized that such data, as we had intended using it, were essentially mean- 



