540 Part IV. Chapter 3. 
6. Ambrosia psilostachya DC. (abundant and gives character to this belt), Distichlis iz 
L., Polygonum ramosissimum Michx., Iva ciliata Willd., Sporobolus heterolepis Gray, Horde 
jubatum L., Seirpus pungens Vahl, Panicum virgatum T Gaura parviflora Dougl., Giyer 
Nutt. 
7. Transition eircumarea on the outer margin of the salt marsh. Iva ciliata Willd., Sporobolus 
heterolepis Gray, Panicum virgatum Gaura parviflora Dougl., Ambrosia psilostachya DC., 
Glyeyrrhiza ER Nutt., Aster sidltihorn: Ait., Helianthus annuus T Erigeron (Leptilon) canad- 
- Acuan illino@nsis Michx.), a fruticosa L., Oenothera biennis L., Physalis lanceolata 
„„ Euphorbia glyptosperma Enge . marginata Pursh., (see oiars XII), Amaranthus 
blitoides Wats., Elymus virginicus L., Akt cynosuroides L., Bei pungens Vahl. 
5. Fresh Water Plants and Wet Meadow Formations. 
Marsh Formation. The four types of this formation are constant only 
when each is subject to certain typic conditions. In other words they exhibit 
numerous gradations through the suppression of proper facies or the intrusion 
of other facies. Certain species of general distribution are of course, common 
in marshes everywhere. Thus Zleocharis palustris is found in the four types 
of marsh, while Ranunculus (Oxygraphis) Cymbalaria is lacking only in the 
false loose-strife association. 
Reed-grass Rush Association. This type of marsh is found in the 
lowlands along rivers an on the flood lands of the principal streams in the 
prairie district. The facies are Phragmites communis, Scirpus lacustris, S. flu- 
watdlis, Typha latıfolia, Alisma plantago and Sagittaria variabilis while Spar- 
gantum eurycarpum, a common element may occasionally assume the impor- 
tance of a facies. Sometimes the individual facies become isolated and these 
are represented in marshy places by one or two facies, sometimes Scearpus 
lacustris or Typha alone, sometimes 7ypla and Sparganium, or Sagittaria and 
Sparganium. 
The most typie of these marshes, as closed formations in which layers are developed, oceur 
along the Missouri River. The primary layer is composed invariably of either Phragmites 
communis, or Seirpus fluviatilis, or both. The secondary layer is constituted by Phalaris arundi- 
nacea and species of Seirpus, viz: S. lacustris, $. atrovirens, $, 2 gens (= S. americanıs). 
Between the clumps formed by Seirpus, Sagittaria, Alisma, Typha an a Span rganium grow. Carex 
lurida occupies the muddy edges; Ca amagrostis canadensis in the shallow pools; Eleocharis 
palustris a dense carpet from the shore throughout the Be broken by yellow patghes of 
Ranunculus multifidus (= R. delphinifolius‘, Ranuncul mbalaria and occasionally by Ranun-. 
culus pennsylvanicus. Herpestis (Monniera) En is a common floating plant while Cieuta 
maculata and Lythrum alatum are found to a limited extent along the Niobrara River. 
Water hemlock Association. This type is found in the sub-sand hills 
under the sandhills proper. The facies are water hemlock Gcuta maculata, 
Asclepias incarnata, Lythrum alatum, and Seirpus atrovirens. — Smartweed 
Association. This is of wide distribution, occuring in wet ravines and can- 
yons. It is never of large extent. The facies are Polygonum lapathifolium, 
P. incarnatum, P.acre (= P. punctatum) and these are not in layers. — False 
loosestrife Association. This occupies broad shallow ditches which are 
