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IOWA ACADEMY OF SCIENCE 
Kunzia tridentata 
Gilia pungens hookeri 
Mentzelia albicaulis 
Phdcelid heterophylla 
Phaeelia sp. 
Erigeron sp. 
EriopJiyllum muUiflorum 
Chaenactis douglasii 
Artemisia tridentata 
Senecio liowellii 
Of these twenty-six species none is of very general distribu- 
tion and none is of more than exceptional occurrence west of 
the Cascades. 
In summing up, we find that there are in all fifty-three species 
that are of very general distribution over the United States, 
or at least within this state, as they are found plentifully on 
both sides of the Cascades, and many of them in all the zones 
represented in Oregon except Hudsonian and Arctic. This wide 
range is due partly to great adaptability, partly to the moisture 
conditions under which they thrive. These forms are merely 
called Transition, but their presence here must be taken as of 
only minor significance in the determination of the zone. 
Omitting those forms of uncertain identification, the rest fall 
into three groups, those characteristic of the Canadian, those 
of the Arid Transition, and those of the Upper Sonoran. The 
Canadian species are very few, and for the most part not abund- 
antly represented by individuals. They are 
Pinus contorta Arctostaphylos manzanita 
Abies nobilis Gentiana simplex 
Jii'iicus regelii Lonicera coerulea 
Eriogonum umbellatum Erigeron armeriaefolius 
The position of one or two of these even is not very secure, as 
that of Eriogonum umbellatum. 
As we might expect, it is impossible always to distinguish 
sharply between Arid Transition and Upper Sonoran zones, since 
they are not limited by any well marked physical features. So 
far as we can make out, the following are mainly Arid Transi- 
tion forms: 
J uniperus occidentalis 
Pinus ponderosa 
Agropyron spicatum 
J uncus orthophyllus 
Iris missouriensis 
Sisyrinchium bellum 
Sisyrinchium idahoense 
Linum digynum 
Sidalcea oregana 
Taraxia heterantha taraxacifolia 
GayopJiytum lasiospermum 
Gayophytum diffusum • 
Sphaerosciadium capiteliatu rn 
Cicuta occidentalis 
