110 



the Soil Survey, on which the sand is superposed. It is occupied by 

 a sparse vegetation of Ludzigia palttstris and Bleocharis obtiisa. 

 Surrounding it is a zone of Sali.v loiigifolia, now about three feet 

 (I m.) high, and Jidicus acmniiiafiis. (Jutside of this are the usual 

 plants of stabilized blowouts, particularly Oenothera rhoiiibipetala 

 and Lespede:za capitata. This vicinity was studied also in the sum- 

 mer of 1904, and according to the best recollection of the writer, 

 no such assemblage of plants was observed. It is entirely prob- 

 able that the association has developed since that time. Willow 

 seeds may easily have been blown in by the wind, and the seeds of 

 the herbaceous plants may have been brought in in mud on the feet 

 of birds, which were attracted by a temporary pool of water col- 

 lected after rains. 



Not far from this depression there was a similar one, but w'ith 

 sandy bottom. In 1904 it was occupied by Polygoninn acre, Hypcri- 

 ciiiii iinitihnii, Cypenis rk'iilaris, and Jiniciis leiiiiis. In 1908, after 

 a lapse of four years, the deepest part uf the depression had been 

 hlled, so that the bottom was generally level. The prevailing' ^•egeta- 

 tion is blue-grass, Poa pratcjisis, but a few relics of Hypericinn, J un- 

 cus, and Cyperiis still persist. 



Just east of Havana, at the *' Dexil's Hole," there is another deep 

 depression with a more luxuriant growth of vegetation. In the 

 deepest part there is a small but dense thicket of Sali.v longifolia. 

 Under the willows the sand is cox'ered with a carpet of moss and 

 decaying leaves, making a humus layer which must aid greatly in 

 the absorption and retention of water. At the edge of the thicket 

 is a narrow zone of Bochincr'm cylindrica, Ludvigia alfcrnifolia, 

 and Lycopiis auicrkaiius. These ])lants may be considered as 

 a part of the Salix association but do not live within the thicket 

 because of the weak light. Around the willows, and extending 

 partly up the hill, is a dense growth of Solid ago graininifolia 

 and Bquisctuni hyemale, var. infeniiediinn, constituting the Solidago 

 association. The two alternate, Hqiiisetuui occupying about one 

 third of the zone. Mingled with these are a few plants of Cacalia 

 atriplicifolia, Vcrnonia fasciciilata, and Asclepias s\riaca, as well as 

 a number of the usual blowsand i)lants, as Paspaliun setaceiini, Cas- 

 sia Chaiiiaechrista, Crisfafella Jaiiiesii, Croton glaiidulosiis, var. sep- 

 teutrioiialis, Ambrosia psilostachya, and Monarda punctata. Bra- 

 grostis trichodcs, Chrysopsis inllosa, and LitJiospenninii angustifoHuni 

 also occur, but are rare. This zone has a vertical width of about six 

 feet (2 m.). Near its upper (outer) margin are a number of old 

 bunches of Sporobolus cryptandrus and a few of Andropogon fur- 



