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S. B. PARISH 



ing a basis for future comparisons, but it has certain peculiarities 

 which are of interest in themselves. 



The introduced plants of the Valley are composed of three 

 classes, distinguished by the sources from which they are derived. 

 Those of the first class number but two species, which have been 

 within recent years brought in from the eastward by the Southern 

 Pacific Railway and distributed, not only in this Valley, but 

 throughout southern California. One of these, Trihulus terres- 

 tris, is everywhere common about railway stations and yards, and 

 in many places has spread into the streets of the towns. The other. 

 Solarium eleagnifalium, is quite common in like places, but al- 

 though it enjoys the advantage of an earlier introduction, it is 

 neither as ubiquitous not as abundant as the other plants intro- 

 duced by irrigation. 



There are a number of plants which are indigenous in the bot- 

 tom lands of the Colorado River, and in its delta, most of which 

 also grew about the lagunas and salinas which formerly existed 

 in the Valley, which have now, as a sequence of irrigation, become 

 the most abundant, the most widely spread, and the most obnox- 

 ious weeds with which the Imperial farmer has to contend. In 

 some cases they have come from the drained lagoons which are now 

 turned into farms, but for the most part they have been carried 

 in by the irrigation water, and thus sown over the fields. In the 

 same way have entered a few weeds which grow in the bottom 

 lands at the intake of the main irrigation canal, but which are not 

 known elsewhere in California. It is evident that this is a most 

 effective means of dissemination, for the seeds are deposited upon ' 

 the moist bed left by the irrigation, so well adapted to facilitate 

 their germination. In crops cultivated by plow or hoe the young 

 weeds may be destroyed, but much of the land is devoted to alfalfa, 

 and here they are checked only by mowing, which in most cases 

 is ineffectual. 



A novel method of road-making which is practiced in the Valley 

 has a tendency to establish and maintain roadside weeds. It is cus- 

 tomary on the most traveled highways to throw up a considera- 

 ble ridge of earth through the center of the roadway, and when one 

 side becomes cut up and dusty by travel, it is flooded from the irri- 



