24 BULLETIN 211, U. S. DEPARTMENT OF AGRICULTURE. | 
Of more importance is a group of introduced weeds, about the 
probable effects of which we know less and whose spread within 
recent years has been rather ominous. These are mostly tumble- 
weeds, of which the Russian thistle (Salsola pestifer) is far and away 
the worst. (Pl. VII, fig. 1.) Their seed-distribution habits are. 
admirably adapted to an open country with strong winds, and they 
scatter their abundant crops of seed over wide areas. Most of the 
species are able to endure extreme drought and great heat; their 
seeds germinate readily and the seedlings endure very unfavorable 
conditions and grow into plants that mature seed whether they be 
but a few inches high or reach maximum size. They practically all 
belong in the goosefoot or amaranth families and have to their credit 
the fact that they are all to some extent valuable as forage when 
young, and they are eaten when nothing better is available. 
In regions having a rainfall of over 15 inches the Russian thistle 
is very much at home, and wherever the native grasses have been 
kalled out either by stock or by the plow it is a pestiferous weed. 
For a short time, while it is young and tender, it is a fairly good 
feed, and it has been used as hay and silage when other crops have 
failed in the dry-farming regions; but these uses are always make-- 
shift attempts to utilize a product that is not desired. Ordinarily, 
it does not seem to be able to crowd out the native grasses, but in 
the dry-farming areas, where the sod has been broken and the land 
deserted for any reason, it usually takes the ground completely. It 
also takes badly overstocked places on the ranges, especially where 
sheep have been held too long. Whether the native grasses will be 
able to crowd their way back into such areas or not still remains to 
be seen. If they are not, then the importance of this pest is in- 
creased many times. 
Certain poisonous plants are also of some considerable menace to 
the ranges, especially where any overstocking is going on. Speaking 
very generally, these plants form a very small and numerically unim- 
portant part of the natural flora until the factor of overstocking 
enters. Of course, the different species differ in importance merely 
on the basis of the readiness with which they reproduce themselves 
and their ability to compete with their plant associates. Under 
normal conditions, unless pressed by hunger, grazing animals of all 
kinds let them alone and hence do not in any way interfere with 
their natural rate of reproduction and spread. Like other weeds 
that are not eaten, they thus tend to spread much more rapidly 
when relieved of their plant competitors by the animals. In fact, 
under these circumstances there is nothing left but their animal and 
plant parasites to hold them in check, unless man should interfere.’ 
is now the custom in certain localities for the herder to carry a spud or a spade, dig these plants up, collect 
them, and burn them. The practice evidently pays or it would not be followed. 
