92 



The Plant World. 



A good prickly pear of any kind must be, first of all, a rapid 

 grower; this is the all-important consideration. The chemi- 

 cal composition of the plant may be left entirely out of account, 

 for the rapid-growing spineless forms do not differ enough in 

 composition to make it worth while to consider that feature. 

 The permanency of the spineless character is of much importance, 



Fig. 7.— A young plant of a yellow-fruited "spineless" and seedless species of 

 prickly pear from the Island of Malta. Reproduced by courtesy of the Bureau of 

 Plant Industry. 



and since all "spineless" prickly pears are more or less spiny, 

 it is to be expected that under certain conditions they will be- 

 come more so. From investigations thus far conducted it seems 

 that hard, unfavorable conditions, such as alkalinity of the soil, 

 extreme heat, drouth, and possibly low temperatures, contribute 

 to increase the spines of the nearly smooth opuntias. But while 

 this is true, observations thus far made do not indicate that there 

 is any probability that the spines or spicules will increase until 

 these prickly pears will require singeing before cattle can eat 



