Jennings : A Botanical Survey of Presque Isle. 363 



Besides this alternation of consocies the formation also exhibits 

 layering and zonation within itself. 



On the outside of the mature Rhus-AI>ius zone, and often leading out 

 into the Fopulus zone, there is usually a low shrub zone characterized 

 by Myrica carolinensis, Rubus allegheniensis, and Solidago canadensis, 

 the whole often being overgrown with Vitis vulpina. On the inside 

 of the tall RJms-Alnus zone there is again a secondary zone, which 

 is often rather complex in structure. Principal among its species, 

 besides young plants of the facies, are Myrica, Solidago canadensis, 

 Cormis stolonifera, Cornus amomuvi, Salix discolor, and Salix nigra. 



Where the facies forms a closed structure, the forest-cover is so com- 

 plete, that none of the plants the disseminules of which reach this loca- 

 tion, aside from certain fleshy fungi, Russiila emetica, Lactarius piper- 

 atiis. Boletus sp., etc., which form a transitory ground layer, are 

 able to accomplish ecesis, and the dark pper soil is in places en- 

 tirely devoid of vegetation. With the death of some of the facies, 

 or where the forest-cover is not so complete, there is a rather weak 

 secondary layer consisting usually of the species which constitute the 

 inner secondary zone. 



Stage G. — Lagoon B, Eb, and Marsh 3.'* 



In Marsh 3 (see Plates XLIX and L) the central portion of the 

 lagoon is now entirely filled up and has progressed to the Calatna- 

 grostis canadensis consocies of the Cladiuni- Calamagrostis formation. 

 There is much Dryopteris thelypteris and some Scirpus cyperinus, and 

 in a depression at one end there is a small clump of Typha latifolia, 

 a relict of a former consocies. Several of the Compositae of the 

 Cladium-Calamagrostis formation are also present. The shrub-zone 

 is encroaching on the meadow very rapidly, and at one end of the 

 meadow there is now only a narrow lane between the shrub-borders, 

 so nearly have they approached each other. Some of the last meadow 

 species to disappear among the advancing plants of the shrub-forma- 

 tion are Eupatorium perfoliatmn and Scirpus cyperinus. Solidago catia- 

 densis increases in abundance among the smaller shrubs, especially the 

 Myrica of the inner secondary zone of the Rhus-Alnus formation. 



Lagoon Eb, a small oblong pool near Long Ridge, now about 

 thirty feet long, presents the following rather fragmentary structure : 



"*The three small marshes immediately north of Horse-shoe Pond are spoken of, 

 consecutively from north to south, as Numbers i, 2, and 3. 



