DISCOVERY OF THE ANCESTRAL FORM 

 OF DAHLIA JUAREZII 



W. E. SafI'Ord 

 U. S. Department of Agriculture, IVashiugton, D. C. 



IT IS a well-established fact that we 

 owe all of our beautiful cactus da- 

 hlias to a single plant, which was 

 sent to Europe from some unknown lo- 

 cality in Mexico about the year 1863. It 

 bloomed for the first time in 1864 and 

 was figured in the Gardeners' Chron'cle 

 in 1879. By the cross-pollination of this 

 plant with the types of dahlias previ- 

 ously cultivated, many beautiful forms 

 resulted. From these have descended 

 the varieties which we now call cactus 

 dahlias and hybrid cactus dahlias, all of 

 which are characterized by long florets, 

 with their lateral margins turning back- 

 ward instead of forward. 



According to the accepted classifica- 

 tion of (cactus) growers, Z)fl/i//a juarezii 

 would be called a hybrid cactus dahlia. 

 It resembled in all respects the variety 

 called Kalif (Fig. 23). The ancestral 

 wild form, with a single row composed 

 of eight rays, remained unknown until 

 October 21, 191 6, when it was dis- 

 covered by Wilson Popenoe, of the 

 Office of Foreign Seed and Plant In- 

 troduction, while on a mission to Guate- 

 mala. This primitive species was de- 

 scribed and figured by the writer in the 

 Journal of the Washington Academy 

 of Sciences, vol. ix, pp. 369 and 370, 

 July 19, 1 91 9. It was named Dahlia 

 popenovii, in honor of its discoverer. 

 Its long, spreading, crimson rays, revo- 

 lute, or turning backward along their 

 margins, can be compared with those of 

 the well-known Dahlia coccinea, which 

 is shown with it in the accompanying 

 field photograph made by Mr. Popenoe 

 near San Lucas, Department of Zacate- 

 pequez, Guatemala, October 21, 1916. 



The specimen of Dahlia coccinea in 

 Mr. Popenoe's photograph is an exact 

 facsimile of the original type specimen 



figured by Cavanilles in 1794, except 

 that it has eight instead of n.ne rays. 



In Mr. Popenoe's notes, dated An- 

 tigua, Guatemala, October 23, 1916, is 

 the following entry : "On my way back 

 from Guatemala Gity to th's place I 

 collected some wild dahlias about twcj 

 kilometers above Santa Lucia, at an 

 approximate elevation of 6,600 feet, 

 where the plants were most abundant. 

 I have not seen them as low as 5,000 

 feet, but have found them up to 7,000, 

 which is as high as I have gone. I do 

 not know how much higher they may 

 occur. The plants observed near Santa 

 Lucia grow to a height of about four 

 feet. The stem is a dull greenish pur- 

 ple to purplish green, usually glabrous 

 but sometimes with scattering hairs 

 toward the upper portion. Leaves 

 twice-pinnate near the base of the stem, 

 once-pinnate or simple above ; leaflets 

 of the lower leaves ovate acute, two and 

 a half inches long, one and a half inch 

 broad, remotely dentate, sparsely fur- 

 nished with short bristly hairs, which 

 are more scant beneath ; rachis not ex- 

 ceeding five inches in length, often verv 

 short ; petioles absent to three-fourths of 

 an inch long. The flowers are two to 

 three and a quarter inches broad, with 

 eight- rayed florets, the latter sterile and 

 orange brown or crimson in color, in 

 some forms short and broad, in others 

 long and narrow with the margins re- 

 curved or revolute, giving to the flower' 

 the appearance of a cactus dahlia, and 

 contrasting with the other form having 

 broadly spreading flat rays rounded at 

 the tips." 



DaJilia juarezii, the ancestor of all 

 our cactus dahlias, like DaJilia pinnata, 

 the type of the genus, was described 

 from a hybrid plant growing in a state 



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