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1897] NEWS 233 
studied the Rocky mountain flora have frequently commented on the interest 
attached to the plants from an ecological standpoint, but most perplexing to 
the systematist. It is not strange that this should be the case, since there 
are great differences in altitude and soil and the relative humidity of the air 
varies greatly. This is a most prominent factor in the development of plant 
life. A cursory glance at the plains flora of eastern Colorado shows that 
there are representatives of a flora common from Texas to British America, 
and east to Indiana. We should not for a moment suppose that the species 
are identical in structure, since the conditions under which they occur are so 
different. Attention was called to the great abundance of plants dissemina- 
ted by the wind, as Cycloloma, Salsola, Solanum rostratum, Populus, Cer- 
cocarpus, “ fire-weeds"' (Epilobium spicatum and Arnica cordi tfolia), Hordeum 
*ubatum, Elymus Sitanion, etc. Plant migration may be studied to better 
advantage in the irrigated districts of the west than elsewhere, partly 
because the water carries many seeds and fruits in a mechanical way and 
partly because the soil is very favorable for the development of plants. 
Instances were cited where several foreign weeds are becoming abundant, as 
Tragapogon porrifolius and Lactuca Scariola. The latter, known as an intro- 
duced plant for more thana quarter of a century, is common at an altitude 
of 7500 feet in Clear creek cafion. Once having become acclimated, it is 
€asy to see how prickly lettuce is widely disseminated. 
ollectors appreciate the great importance of giving more attention to 
conditions under which plants thrive, such as phases of development, soil, 
climate, and altitudinal distribution. Structures of plants are produced to 
meet certain conditions. Under extreme conditions protective devices are 
more pronounced. In discussing some of the plants, Warming'’s classification 
into hydrophytes, es eH halophytes, and mesophytes, was adopted. 
The mesophytes of eastern lowa were compared with some of the a 
of western Iowa, such as Yucca angustifolia, Mentzelia ornata, Liatris 
fata, etc. These increase in numbers in western Nebraska, and attain 
maximum development in northern Colorado. In the fondly ead moun- 
tains the mesophytes constitute a large class, although xerophytes are.com- 
wieeet in the dry, —— sunny places. The photosynthetic system is reduced 
_ to guard again ion which would otherwise take place at 
high altitudes. The thick rootstock of pee dry, open places is a 
_ an admirable protection against drouth and cold. In cafions where snow — 
een ee oe come plants do not need this ciation pein pt % 
