102 RrEED: MEADOW VEGETATION IN NORTHERN COLORADO 
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WATER REQUIREMENTS OF VARIOUS PLANTS 
_ The plants of the meadows may be classified according to 
their usual water requirements or better the amount of moisture 
in the soils they frequent. Following a plan used by Professor 
Ramaley in his lectures on ecology, the meadow plants are given 
the index numbers 5, 6, and 7. Those that grow most commonly 
in the drier parts of the meadow are numbered 5, those in the 
wettest parts 7, while the typical mesophytes are numbered 6. 
In meadows that are along streams or ponds it is often possible 
to recognize about three zones, these being characterized by dif- 
ferent amounts of moisture in the soil. Some plants are restricted 
to a single zone while others may grow in two or more but, with few 
exceptions, not in equal abundance. Certain plants, as Achillea, 
grow well in all three zones but are seldom in great abundance 
anywhere. 
In the systematic list of meadow species given below the 
relative soil moisture with which the various species are usually 
associated is indicated by one or more of the figures 5,6,or 7. The 
figure which represents the normal condition for the species is — 
italicized. 
DURATION OF INDIVIDUAL PLANTS 
The majority of the meadow plants are perennials living for 
many years. Thirteen species, representing nine per cent. of 
the flora, are annuals. These are Polygonum Englemannii, Alsine 
baicalensis A. longipes, Draba nitida, Epilobium paniculatum, 
Gayophytum ramosissimum, Androsace subulifera, Amarella plebeja, 
Chondrophylla Fremontii, Collomia linearis, Collinsia parviflora, 
Orthocarpus luteus, Rhinanthus Crista-galli. Five species, repre- 
senting three per cent. of the flora, are biennials. These are Allium 
