"REVERSION" IN PRICKLY PEARS 



Origin of All Spineless Varieties of Opuntia to be Sought in Long Selection From 



Spiny Ones — Plant May Produce Spiny Joints on One Side 



and Spineless Ones on the Other.' 



David Griffiths, 

 Ai^riLitltitn'st, Office of Farm Management, Bureau of Plant Industry, C S. Depart- 

 ment of Agriculture, Washington, D. C. 



IN THE economic handlin^^ of the 

 ])rickly pear as a farm crop in 

 southern Texas great differences 

 have been found in the ease with 

 which spines arc burned from different 

 species, and the differences are to a 

 considerable extent matters of geo- 

 gra]jhical position. Native species from 

 the immediate \'icinity of Brownsville 

 have been employed in our economic 

 plantings, because it was early recog- 

 nized that these were the best adapted 

 to the conditions and would make the 

 largest tonnage of any that could be 

 grown. 



All species of this region are exceed- 

 ingly spiny. They arc even more spiny 

 than those of the San Antonio region; 

 moreover, the spines remain green for 

 a longer period and are consequently 

 much more difficult to singe properly 

 prcj^aratory to being fed. This is a 

 serious economic consideration and one 

 which is difficult to prevent. Under 

 the humid conditions of the coastal 

 region the tendency is for the spines 

 (fig. 13, a) and the spicules (fig. 13, h) of 

 all species to become dry much more 

 slowly than in the more arid atmosphere 

 of the regions farther inland. 



In the cultivatifjn of this crop it is 

 therefore necessary for one to choose 

 between the spineless forms not needing 

 singeing and the much more productive 

 s])iny native varieties, which are not 

 only difficult but often imj^ossible to 

 singe ]jroperly. It may be ])ossil)le in 

 time to breed varieties better ada])te(l 

 than the native ones, bvit the develo])- 

 ment of such fomis from the s])iny 



native ])rickly pears of the delta of the 

 Rio Grande is an almost hojjclcss task, 

 the \'ariation in the number of spines 

 produced being so trifling as to scarcely 

 warrant selection, while they do not 

 appear to hybridize readily with the 

 spineless forms. 



In June, 1905, the Office of Foreign 

 Seed and Plant Introduction of this 

 Bureau received from Dr. G. Borg, 

 San Giovanni, Island of Malta, a few 

 cuttings of a large spineless species, to 

 which was assigned vS. P. I. No. 14807. 

 The plant passes in both this country 

 and the Mediterranean region as spine- 

 less. About half a dozen cuttings of 

 this importation were planted and grew 

 for two and a half years at the plant 

 introduction field station at Chico, Cal. 

 They were then cut up into indi\'idual 

 joints and re-established in nursery form 

 in a ]jlantation as extensive as the stock 

 thus produced would permit. It was 

 noticed that one of the original plants 

 had on one of its joints three or four 

 spines in one or two pulvini on one side. 

 No heed was paid to this, however, and 

 this joint was lost sight of in the ])lant- 

 ing, which was made in nursery form. 

 In other particulars this did not differ 

 from the oIIkm" plants. 



This i)riekl\' pear belongs to what 

 commonl\- i)asses for Opuntia ficus 

 indica and is nearly si^ineless. Frc- 

 ciuently short spines are j^roduced, but 

 tlv\v are very few in number; there is 

 l)ut one in an areole, and they arc 

 usually only two to five or six milli- 

 meters in length. It is on the whole an 

 average of tlie spineless forms. Wlien 



'This article is an extract from Mr. (jriflith's Bulletin No. 31, U. S. D. A., "Behavior, under 

 Cultural Conditions, of Species of Cactus Known as Opuntia," Washington, Decemlier 30, 1913. 



222 



