14 BULLETIN 31, U. S. DEPAKTMENT OF AGEICULTUKE. 



account of the deterioration and unsightly condition which comes on 

 after a few years. However, this condition is not found in all of the 

 species, but it does obtain in the low, prostrate, and bushy forms 

 with which growers have had the most experience. A very large 

 proportion of the species are trees and grow indefinitely as such. 

 The low forms, on the other hand, have a tendency to die out in the 

 center and have to be reestablished by terminal cuttings; or, as is 

 usual in nature with many species, the main limbs resting on the 

 ground strike root and continue to extend the plant in all directions. 

 This is especially true of the small and northern forms and implies 

 that the plants deteriorate in such a way as to become unsightly, if, 

 indeed, they are not often threatened with a worse fate in a few 

 years by dying outright. This is exactly what takes place with many 

 of the small species which are grown in conservatories. The older 

 portions of the plants die and the younger portions, radiating out- 

 ward from the old center, establish themselves by striking root and 

 become really independent plants but very unsightly. 



In some species, most notably that known to the botanist as Opuntia 

 par-ryi and its allies from the California-Nevada Desert, wherein the 

 joints are club shaped and bent into a semicircle, the connection with 

 the old parent plant is not broken, at least not 2or a long time. The 

 center dies to all appearance, like the other Ic ,v species, but in fact 

 only the upper portion of the joint dies and the lower portion, form- 

 ing a hard, woody cord, continues to live indefinitely and connects 

 the successive joints of the radiating arms. This gives the plant a 

 still more ragged appearance. 



Conditions apparently affect the age of certain species at least, 

 and at times those which grow naturally for a great number of years 

 in their natural habitat behave very differently when placed in a 

 different locality and under different conditions. Opuntia spinosior, 

 for instance, from the deserts of Arizona, is not considered a par- 

 ticularly short-lived species. It is very slow of growth and cer- 

 tainly an estimate of 15 to 20 years would be modest for its lease of 

 life. It grows rather freely from cuttings at San Antonio and is 

 exceedingly rapid in its development, commonly attaining a height 

 of 4 feet in two years, blossoming sparingly the second year 

 and very profusely the third, but the plants are almost invariably 

 dead by the end of the fourth season, although they may reestablish 

 themselves from self-made cuttings. This phenomenon is a very 

 peculiar one but appears very regularly and has now happened with 

 six distinct plantings. The outer tissues turn brown and this finally 

 extends over the entire plant, beginning at the ground. This be- 

 havior is universal with this species in this situation and is confined 

 to it, no other species apparently being affected in exactly the same 

 way. Our plants have been secured from Arizona, from La Mortola, 



