98 KANSAS UNIVERSITY SCIENCE BULLETIN. 



of the great care taken in obtaining it. Many thanks are due 

 Mr. Peace on this account, as well as for numerous verbal ex- 

 planations and descriptions of the desert, the vegetation and 

 the individual plants. 



The literature dealing with the desert plants is, as is well 

 known, somewhat meager. So far very little more than a de- 

 scription or a mere mention of KoeherUyiia has been found. 

 Gray describes it in his Plantse Wrightiana^, and places it 

 with the Rutacese. Engelmann mentions it twice in his works : 

 once in his review of the Wislizenus plants and once as erro- 

 neously numbered by Emory among his Cactacese of the South- 

 west. Bentham and Hooker describe it under the family 

 Simarubacese. The Ailanthus, or "Tree of Heaven," is perhaps 

 the most familiar representative of this family with us north- 

 ern dwellers among mesophytic forms. John Charles Van Dyke 

 alludes to the "crucifixion thorn" in "The Desert." He says he 

 has met with it in several localities although it is reported as 

 "very scarce." Several travelers in Mexico and the Southwest 

 have made collections of this plant or have reported it. Prof. 

 Charles Bessey, of the University of Nebraska, in the "Burro 

 Thorn" (Holocantha emoryi) finds a plant of great interest, if 

 not one wholly as attractive morphologically, if one may judge 

 by the brief account he was able to give for lack of the "oft 

 promised material." 



A description of the plant as a whole has not been found. 

 We do not know that anyone has ever had the hardihood to dig 

 up a root. It is said to make an impenetrable barrier, so that a 

 plant three feet high is of such dense growth that the main 

 stem is hardly to be seen. Among the earlier collectors of the 

 plant might be mentioned Chas. Wright, Dr. Josiah Gregg, 

 Gen. Wm. H. Emory and Dr. N. Wislizenus. The plant is 

 sometimes called "Junco," It seems as the northern border of 

 Mexico is approached the individual plants become more 

 stunted and less numerous than farther south. The plant is 

 thus described by Sargent: 



"Leaves, not more than one inch long. Flowers, appearing 

 in May and June, about one-fourth inch in diameter. A bushy 

 tree, rarely twenty to twenty-five feet high, with a short, stout 

 trunk sometimes six to eight feet long and a foot in diameter ; 

 more often a low-branching shrub forming impenetrable 

 thickets, often of considerable extent. Wood very hard, heavy, 

 close-grained, dark brown somewhat streaked with orange; 



