190 CLIMAX FORMATIONS OF NORTH AMERICA. 



Shaw (1902) has studied the development of vegetation in small swamps at 

 Wood's Hole. The body of the pond contains no plants as a rule, but there 

 are two zones of flowering plants around the shore: 



The inner one consists of lAmnanthemuin lacunosum and Lobelia dortmanna, 

 both at depths of 0.6 to 3.9 m. With them occurs Gratiola aurea, but it did 

 not appear to flourish. Between this zone and the shore-line zone of Solidago 

 graminifolia is a space of open water, probably caused by the action of the 

 waves in shallow water. In some of the shallower ponds Nuphar and Ponte- 

 deria form dense beds, and the Solidago zone is interrupted by Lysimachia, 

 Lycopics, and Coreopsis. The general succession in such pools is begun by 

 Nuphar and Nymphaea, though in some cases Idmnanthemum, Brasenia, and 

 Hypericum take a leading part in building the floating-mat vegetation. Sev- 

 eral species of Utricularia aid in this process, as well as Sphagnum, Carex, 

 Xyris, and Drosera. Decodon vertidUatus plays a leading part in giving firm- 

 ness to the growing mass. It forms stools upon which occur a large number 

 of swamp shrubs, Clethra, Azalea, Vacdnium, Ilex, Myrica, Andromeda, etc., 

 which rapidly transform the floating-mat into a swamp-thicket. Decodon dis- 

 appears and after a time the trees, often wholly Chamaecyparis, appear, and 

 the vegetation becomes a swamp-forest. The author concludes that in some 

 cases the activity of vegetation in the filling of ponds is secondary to sedimen- 

 tation. The vegetation of an open morainal pool, though undrained, may be 

 purely hydrophilous. Xerophytic conditions appear about the time of the 

 formation of the floating-mat. 



Ganong (1903 : 349) has studied the successional relations of the communities 

 of the salt and diked marshes of the Bay of Fundy: 



The consocies of Spartina stricta occupies a belt just above and below the 

 high-tide level. It succeeds the Salicornia-Suaeda associes in this belt, but 

 is replaced above by the Staticetum, which is characterized by lAmonium caro- 

 linianum and Spartina juncea. This associes covers the highest salt marshes, 

 such as are rarely oveiiowed, and represents the final condition of the salt- 

 marsh vegetation. The wet-marsh formation consists of the Spartina cyno- 

 suroides association, and the Carex-Aspidium association, in which the latter 

 is properly a transition from the Carex-Menyanthes bog to the Spartinetum. 

 In reclaimed diked marshes the sere is held in a grassland subclimax by culti- 

 vation. This consists of Phleum and Agropyrum typically. The general 

 sequence of the sere is indicated by figure 4. 



A6R0I>YRUM CCOUCM) 

 / .HORDtUM 



Weeds / / ,5tatice 



AtRIPLEx/ / / / STATtCtTUM 



Spartinetum//// / [ Spartinetum 



CaRICETUM AsPIDETUM MACROSPARTINETUM PHLEOMETUM ! / ■' / / / I \Seose-boq 



* ', • til .X . • • ^ \ 



A ! ! ■ Jr V i /V^ /^--ju^\. 



Fig. 4. — Section of salt and diked marshes of the Bay of Fundy. After Ganong. 



Harvey (1903 : 29) has indicated the general features of the water prisere in 

 the ponds of Moimt Katahdin, Maine: 



The submerged community is absent, and the floating stage is poorly 

 developed, consisting of Potamogeton confervoides, Nuphar odorata, and iVj/m- 

 phaea kalmianum. The amphibious zone is composed of Isoetes, Zizania, 



