THE PLANT WORLD 233 



Rushville, on the road to Pine Ridge Agency. The racemes are less 

 developed than in moister climes, otherwise they are splendid speci- 

 mens. Other less notable discoveries might be enumerated, but I fear 

 to trespass ui^on valuable space. I have but one explanation for these 

 rarities, viz.: that we lack trained observers to see, identify and report. 

 From what I have found I have reason to believe that I have only made 

 a good beginning of what is to be found, and that such plants as I have 

 here reported are scattered here and there all over our wide domain, 

 waiting for those who have eyes to see. — J. M. Bates, Callaway, Neb. 



Struggle for Existence among Plants. 



The stud}' of those plant-formations that owe their origin to the 

 disturbances set up by man incident upon his cultivation of the soil, 

 affords an interesting field for observation. The breaking of the soil 

 and destruction of native species opens the way for the introduction of 

 new species particularly suited to the prevailing conditions. A waste- 

 formation is the result, and the composition and character of such for- 

 mations vary with local conditions. 



On the vacant lots in Stillwater, Oklahoma, it is not unusual to 

 find very compact waste-formations composed entirely, in some cases, 

 of Prionopsis ciliata, one of the Compositae. This is a rather widely 

 distributed plant throughout Oklahoma and the Southwest, and assumes 

 ill many localities the character of a rather important weed. A vacant 

 lot was selected, on which the plant covering was composed almost en- 

 tirelj^ of this sj^ecies, for the purpose of determining by accurate counts 

 tlie number of plants per square meter of area. A total of 4038 plants 

 were found on an area of exactly 100 square meters, the average num- 

 ber of indi^dduals per square meter was therefore found to be 40! 



Counts Avere made to determine the average number of heads per 

 l')lant, and this average was found to be 7.5 on the 100 square meters; 

 therefore there were 30,225 heads, or an average of 302 heads per square 

 meter! On the entire area not to exceed a dozen live plants of other 

 species were found on September 1st, distributed among the following 

 species: Panicam capillare, Ambrosia artemisiaefolia, and an undeter- 

 mined Polygonum. Surely this may be considered a tyi:)ical example of 

 a " closed " formation. The perfect adaptation of this plant to the ex- 

 tremely arid conditions prevailing in the region throughout the sum- 

 mer, had enabled it to outlive the few plants even that had survived the 

 severe struggle for existence that occurred early in the season. — E. Mead 

 Wilcox, Alabama Polytechnic Institute, Auburn, Alabama. 



