78 HARPER 



The modes of dissemination for these plants are not very well 

 known. About half a dozen species have seeds transported 

 by the wind, and two or three of the woody plants have drupes. 

 There are a few instances of resilient stems (" tonoboles"), but 

 these obviously would not scatter seeds from one pond to 

 another. Probably as many seeds are carried on the feet of 

 aquatic birds as in any other way. 



Taxonomically the list contains 52 species belonging to about 

 38 genera and 26 families. Cyperaceae is the largest family, 

 as is often the case, and Compositae next. There are only two 

 species in the list between Euphorbiaceas and Juncaceae, and 

 none between Polygalaceae and Saururaceas. Rhynchospora 

 is the largest genus here, as in many other habitats. Nearly 40% 

 of the angiosperms are monocotyledons. 



These cypress-pond plants are quite restricted in range, doubt- 

 less because similar habitats are not very widespread. About 

 half the species are confined to the pine-barren region, and 

 only about 10% extend farther inland than the fall-line. Only 

 about 35% range as far north as Virginia, in the coastal plain or 

 otherwise. Seven species are reported from the tropics, but 

 perhaps not correctly in every case. All but one or two have 

 been reported from Florida, and they probably all grow in the 

 flat pine-barrens of Southeast Georgia, where cypress ponds are 

 common. A few are not known farther inland than the Altamaha 

 Grit escarpment, but the majority range nearly throughout the 

 pine-barrens of Georgia (as the typical species, Taxodium im- 

 bricarium, does). Almost none of them are reported up the 

 Mississippi valley even as far as Arkansas. In this respect there 

 is a marked contrast with the group just preceding this. 



There is probably not a phytogeographical unit in the whole 

 region more stable than the cypress ponds. While the glacial 

 ponds in the north last only a very short time, geologically 

 speaking, the cypress ponds probably have not changed materially 

 in thousands of years, barring the works of man and possible 

 climatic changes. Erosion is of course out of the question, and 

 the quantity of humus (the principal factor which determines 

 the life of a glacial pond) probably does not vary much, for the 

 fires which get into the ponds occasionally in dry seasons doubt- 



