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O. A. STEVENS 
absent still. Sonchus arvensis he does not mention, it having been intro- 
duced in Manitoba a few years later and being now common through the 
valley and spreading farther. 
Neslia paniculata and Camelina saliva seem to be restricted mainly to 
the northeastern two or three counties, Camelina dentata being widely dis- 
tributed in flax. Certain Poaceae are especially abundant and charac- 
teristic: Avenafatua, Hordeum juhatum, and Agropyron repens. Chaetochloa 
glauca, C. viridis, Echinochloa crus-galli, and Panicum capillar e are also very 
abundant but perhaps less characteristic. Syntherisma sanguinalis is 
repeatedly introduced in southern-grown millet seed but has not been col- 
lected in the state even in adventive condition. Plantago lanceolata has 
been collected a few times but apparently does not become established. 
Comparison with the Biological Survey Reports 
Considerable difficulty has been found in trying to correlate the distribu- 
tional data with those of previous publications dealing with life zones. The 
Rocky Mountain region has been described in considerable detail, but in 
the plains region, as noted by Cary (6), the zone limits are less well marked. 
Trees have been used to a great extent in indicating the boundary lines of 
the zones, and North Dakota is especially lacking in trees. 
Pinus scopulorum is mentioned by Cary (5) as "the characteristic 
Transition tree," but in North Dakota it is found only on the hills in the 
extreme southwestern part of the state where the Austral Zone invades the 
river valleys. Populus tremuloides, according to the same author, "is 
perhaps the best characterizing tree of the Canadian Zone" in Wyoming 
(6). He also mentions it as "restricted to the Canadian Zone" in Colorado, 
while Bailey (2) lists it for the same in New Mexico. Apparently it is 
most abundant in this zone east of the mountains, but it is common through 
the Transition Zone and extends half way through the Upper Austral in the 
Mississippi Valley region. Querciis macrocarpa is noted as growing in the 
Transition Zone in Wyoming (6), but in the Mississippi Valley region where 
it is more abundant it extends from the Canadian southward well into the 
Lower Austral. 
Of the trees and shrubs listed by Cary as Upper Sonoran in Wyoming, 
at least Salix amygdaloides, S. fluviatilis, A triplex argentea, Amorpha nana, 
and Gutierrezia Sarothrae are common in North Dakota Transition, while 
the same may be said of fully one fourth of the "herbaceous plants." In 
the same paper Psoralea argophylla is listed as Transition, although it is 
common on the plains through Upper Austral; Actaea rubra, Sieversia 
ciliata, and Heracleum lanaium, listed as Canadian, are common in North 
Dakota Transition. 
