82 
sloughs along Murdock creek and at the 30th base line. Cow-lily Nympho- 
zanthus variegatus is the commonest species, but there is a dense tangle 
of other aquatics. 
Primary sp.: Nymphozanthus variegatus 
Secondary spp.: Potaviogeton Friesii 
P. praelongus 
P. pusillus 
P. Richardsonii 
P. zosteriformis 
Sagittaria cuneata 
Lemna tnsulca 
L. minor 
Ceratophyllum demersum 
Ranunculus aquatilis var. capillaceus 
R. Purshii 
Myriophyllum exalbescens 
The water is only 1 or 2 feet deep over a thick accumulation of vege- 
table remains in the form of black muck. The level is subject to consider- 
able fluctuation during the summer season, so that in July and August such 
aquatic plants as the cow-lily and the arrow-leaf Sagittaria cuneata grow 
as emergent vegetation on the semi-dried substratum. 
SHORE ASSOCIATIONS 
As already stated, slough margins have much in common with the 
marshy shores of low river flood-plains and deltas. Their main divisions 
consist of a zone of emergent aquatic plants which have well-developed 
rootstocks colonizing submerged peaty materials, and a zone of sedges and 
grasses which forms a transition to the surrounding meadows. These have 
their simplest organization in partly ponded places like Murdock and Cree 
creeks, where the first zone is nearly all Equisetum limosum, and the second 
is a close growth of Carex rostrata wuth Sium suave occasional. Near the 
mouth of Cree creek the inter-relationship between this type of shore and 
that of the delta margin is clearly seen (Figure 12, C). Scirpus validus , 
a lake shore plant, is in an association with Typha latifolia , a pond margin 
species, and enclosed between zones of Equisetum limosum and Carex 
rostrata. 
In slough ponds the emergent aquatic association is quite variable in 
its floristic content, not only in different ponds but also around a single 
pond. At the 30th base line a dense growth of the cress Rorippa palustris 
surrounds the water, advancing into it with an abundance of floating seed- 
lings. Following this is a zone of Eleocharis palustris, and then one in 
which Glyceria grandis is the primary species. In similar sloughs at the 
Hay Camp and along Murdock creek Bidens cernua takes the place of 
Rorippa. 
Primary sp.: Bidens cernua 
Secondary spp.: Sparganium eurycarpum 
Sagittaria cuneata 
Glyceria grandis 
Beckmannia Syzigachne 
Eleocharis palustris 
Rumex maritimus var. fueginus 
Ranunculus sceleratus 
Epilobium palustre 
Hippuris vulgaris 
