BEHAVIOR OF SPECIES OF CACTI. 3 



a half years at the plant introduction field station at Chico, Cal. 

 They were then cut up into individual joints and reestablished in 

 nursery form in a plantation 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 planting, which was made in nursery form. In other par- 

 ticulars this did not differ from the other plants. 



This prickly pear belongs to what commonly passes for Opuntia 

 ficus indica and is nearly spineless. Frequently short spines are 

 produced, but they are very few in number; there is but one in an 

 areole, and they are usually only 2 to 5 or 6 millimeters in length. 

 It is on the whole an average of the spineless forms. When the first 

 planting of this stock was grown, one plant which was normally 

 vigorous showed a few rather long spines, as stated above, similar 

 in character to the shorter ones more commonly produced, but much 

 longer and stouter. 



The establishment of the nursery plantation took place in April, 



1908. The following spring all of the spineless forms (especially 

 S. P. I. No. 14807) were cut back to the original cutting for stock. 

 At this time it was noticed that one side of one plant of this number 

 was very spiny and the other side as spineless as the remainder of 

 the importation. With the rest, this plant was cut close, but the 

 spiny cuttings were rejected. In the spring of 1910 the new growth 

 was again in part spiny, and it was again cut back, but one joint was 

 left attached to the original one. At that time neither joint left on 

 the plant showed any spines. 



In the spring of 1911 it was found that the previous season's growth 

 had come mainly from the upper cutting, which grew in the season of 



1909. From the original cutting two joints had sprung, one from 

 each side. All new growth on one side of the plant, whether from the 

 original cutting or from the younger joint, was practically spineless 

 (PI. I, fig. 1), while the other side was exceedingly spiny (PL I, 

 fig. 2), the latter resembling the more common forms of some of the 

 mission pears grown in all of the collections in southern California 

 and bearing two to four white spines two-thirds of an inch to 1^ 

 inches long. The whole plant is shown in Plate II, fig. 1. 



The appearance of the plant in the spring of 1911 was so striking 

 that it was pruned back but very little, simply enough to shape it up. 

 Several of both spiny and spineless joints were planted, but owing to 

 the condition of the ground when the planting was done all made a 

 very poor growth. However, the small amount of growth that was 

 made came true to the characters of the individual cuttings planted. 

 In the spring of 1912 the previous season's growth was again spiny 



