Griffith: "Reversion'' in 1'RICKL^' J'fars 



223 



SPINES AND SPICULES 



A pulvinus, or cushion of spines (a) and spicules (b), from the edge 

 of a joint of Opuntia lindheimeri from the San Antonio region of Texas. 

 Ordinary "spineless cactus," although it may lack spines, often pos- 

 sesses spicules, Vvfhich make it equally worthle"^s for many of the 

 purposes for which it is sold. It is only the most highly improved 

 varieties that are absolutely free from spicules as well a*-: spines, and 

 hence suitable for feeding to live stock, without first being singed. 

 (Fig. 13.) 



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 char- 

 acter 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 (especiahy 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 loose, 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, 

 while the other side was exceedingly 

 spiny, 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 one and one-half inches long. The 

 whole plant is shown in fig. 14. 



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 



