372 Annals of the Carnegie Museum. 



from above and the hydrophytic forest, which later develops on the 

 muck-soil below. In the pure tamarack forest at the ' ' first Sister Lake, ' ' 

 in the Huron River Valley of Michigan, Weld finds coming in a for- 

 mation composed of almost exactly the same species here included 

 in the Pruniis-Acer formation. 



Stage I. — Ponds R, S, U, V, north end of P. 

 The climax formations of the Lagoon-Marsh -Thicket-Forest Suc- 

 cession, for Presque Isle at least, are to be seen in the Chimney Ponds 

 (R, S, U, and V). The arrangement of the formations at this stage 

 being typically as follows : 



(«) Potamogeton Formation, 

 (^) Castalia-Nymphcea Formation, 

 ■ (^) Decodon-Persicaria Formation, 

 (</) Cephalanthus-Coriius Formation, 

 (^) Rhiis-Alnus Formation, 

 (/) Qiiercus-Acer Formation. 



The ecological conditions obtaining in the Chimney Ponds are 

 evidently very closely similar to those obtaining in undisturbed glacial 

 ponds in the northern states. The Chimney Ponds are quite old and 

 are considerably protected from the winds of the lake by the sur- 

 rounding forest. The accumulation of vegetable matter has been suf- 

 ficient to cause the basins to be fringed and lined with a layer of humus, 

 which by humification has been reduced mainly to the form of a black, 

 semi-liquid muck. The drainage is merely that due to seepage through 

 the porous sand of the peninsula, ordinarily very little water passing 

 either into or out of the ponds, excepting such as is necessary to maintain 

 the water-level against fluctuations due to precipitation, evaporation, 

 or fluctuations in the level of the lake. Even then the seepage is 

 not rapid, and the ponds have on the whole a very uniform water- 

 level. Such exchanges of water must to some extent at least prevent 

 the accumulation of acids in the pond water, and thus at the same 

 time permit the conversion by humification of the vegetable debris 

 into black muck. 



Within recent years several ecological studies have been made of 

 glacial ponds and small lakes throughout the region bordering the 

 Great Lakes. In undisturbed conditions throughout this region the 

 ponds and lakes have practically the same formations, arranged in 

 essentially the same order as has been described for the Chimney 



