323 



of this habitat and its range is much wider than that of bogs. Never- 

 theless, in all the bogs of this region it is one of the dominant 

 species and occupies from thirty to sixty per cent, of the area of the 

 association. The two species that complete the list of the dominant 

 species are given in Transeau's list of the plants characteristic of 

 bogs across northern North America (1903:40-5). Of the two, 

 buckbean {Menyanthes trifoliata) is the more abundant, and may 

 form as much as fifty per cent, of the vegetation in some of the 

 bogs, while Poientilla paliistris is relatively infrecjuent. Secondary 

 species are not common because the Sagittaria and the Menyanthes 

 so occupy the area that very little interstitial room remains. Those 

 that occur most abundantly are bladderwort ( Utricnlaria vulgaris 

 americana), Polygonum arnphibiiim hartzvrightii^ Lysimachia thyrsi- 

 flora, Acorus calamus, and Proserpinaca palnstris. Towards the 

 edge, an invader of the sedge association, Care.v lanuginosa, may be 

 within the limits of the association. In less typical situations, es- 

 pecially those near the railway, where the drainage has been inter- 

 fered with, there are mixtures of this association with species of 

 others near by, the result of which is vegetation of the following 

 composition : Menyanthes trifoliata, Sagittaria latifolia, Utricnlaria 

 vulgaris americana, Scutellaria galericulata, Hypericum virginicum, 

 Bidens trichosperma tenniloha, Iris versicolor, Lysimachia thyrsi- 

 flora and Polygonum mnhlenbergii. In other situations, differing from 

 these, were Acorus calamus, Alisma plantago-aquatica, Oxy polls 

 rigidior, Asclepias incarnata, Polygonum hydropiperoides, and Ltid- 

 vigia palustris in addition to the dominant species. 



Along some of the ditches in the right of way of the Chicago and 

 North Western railway this association is appearing. In most of them 

 the first member to appear is Menyanthes. With it are associated 

 Utricularia vulgaris americana and Proserpinaca palustris. In one 

 case Menyanthes and Proserpinaca were giving way to Spartina and 

 Cephalanthus, wdiich is worthy of mention because the two bushes 

 of buttonbush that occur in this station are the only individuals in 

 this region of a species so characteristic of similar situations in other 

 places. Sagittaria will not as a rule come into these ditches until 

 they are larger in size, and not even then unless there is some move- 

 ment in the water. 



Along the little streams that lead from the bluff towards Lake 

 Michigan, the Menyanthes-Sagittaria association is usually repre- 

 sented by Sagittaria alone. With it may occur a few secondary 

 species, as OxypoUs rigidior, Cyperus fluznatiUs, Alisma plantago- 

 aquatica, Proserpinaca palustris, Veronica anagallis-aquatica, Ranun- 

 culus delphinifolius, Scirpus atrovircns and Penthorum sedoides. 



