52 DISTRIBUTION AND MOVEMENTS OF DESERT PLANTS. 
which have offered a favorable opportunity for continued observation. 
Among the species that have been carefully observed, Evodiwm cicutarium, 
or alfilaria, is of such exceptional interest as to deserve detailed descrip- 
tion. This plant is a native of the Mediterranean region and was intro- 
duced into the New World by the early Spanish explorers. It was 
introduced into Arizona from California, according to Thornber (1906), 
as early as the sixties. At this period numerous freighters brought over 
hay and other supplies, with livestock, to the camps and forts along 
the old road from Ehrenberg to Wickenberg, and thence by other roads 
to points north, east, and south, and along these lines the introduction 
of the plant in question has been observed, as it has gradually spread 
through a large part of southern and southwestern Arizona. It appeared 
in the early seventies in the neighborhood of Oracle, and may have been 
brought from this point to Tucson, though this is not definitely known. 
At all events, it is now well established in various places about Tucson, 
including the Desert Laboratory domain. 
In February, 1906, a careful examination of Tumamoc Hill was made 
for the purpose of locating accurately the points where it had become 
established. As shown by plate 20, it was found to occur sporadically 
from the northeast corner of the domain to points east and south of the 
Laboratory and as far west as the wash. Most of the patches included 
a relatively small number of individuals, in some cases a single one, but 
there were a few areas of considerable extent, notably 5 and 6, where it 
had apparently been established for a period of years, and in places thickly 
covered the ground. Further details of distribution, as observed at the 
time indicated, are deposited in the Laboratory records for comparison 
with what may be observed of the progress of the invasion in future. 
Certain areas, each containing 100 square meters, have been staked out 
for careful observation from year to year. A chart (fig. 1) and a photo- 
graph (plate 21) of one of these indicate in part the method employed. 
The field-notes, which are a part of the permanent record, include the 
list of perennials, their number, size, and position, the distribution of 
the alfilaria on the square, its relation to other annuals, their relative 
abundance and probable competition, and still other matters which will 
facilitate comparison in subsequent years and aid in determining the 
advance or retreat of the alfilaria. 
Another species, Hordeum murinum, is of much interest, since it has been 
possible to observe what are apparently the very beginnings of its inva- 
sion, its habits elsewhere justifying the expectation that large areas of 
Tumamoc Hill will soon be occupied by this pernicious weed, which has 
become established in Tucson and the country adjacent, baffling every 
attempt to eradicate it. 
In April, 1906, an attempt was made to find as nearly as possible all 
the patches of this plant then in existence on the Laboratory domain. 
