50 THE FRUIT OF OPUNTIA FTJLGIDA. 



not a rarity, but a very common occurrence. The fruit of this species is per- 

 sistently green, shows no sign of ripening, and not more than 5 per cent of 

 them have well-ripened seeds. This fruit is pear-shaped, rather slender, 

 smooth, and spineless, like that of 0. fulgida, and has rather prominent 

 areoles. The areoles of the primary flower very often proliferate to secon- 

 dary flowers and the fruits commonly persist over one or more winters. Most 

 of the persistent fruits are single, but chains of two are common and chains of 

 3 or 4 links are not infrequent. The fruits of the upper part of the rather 

 bush-like plant seem always to produce only flowers so long as they remain 

 attached. Many of the fruits of the lower branches, however, often give rise, 

 from one or more up to 6 or 8 of the distal areoles, to rather slender, con- 

 densed branches, bearing numerous prominent areoles ( fig. 95). These con- 

 densed branches, which may also arise on vegetative joints, are vertical in 

 position, are about 4 or 5 mm. in diameter, and 20 to 50 mm. long. If these 

 short branches are left on the plant they may thicken somewhat and become 

 more like the normal, terete, vegetative shoots. No evidence was obtained, 

 however, that the persistent fruit and its vegetative ojBfshoot ever become 

 incorporated into the permanent branch system of the parent plant. These 

 condensed branches apparently play no important part in the development of 

 this opuntia, except when the fruits or the branches alone fall to the ground, 

 there to take root and thus start new plants. 



What has been said of the proliferation of the fruits in the various 

 Opuntias and in Peireskia indicates that each is peculiar in its own way in 

 regard to the ripening of the fruit, in its persistence, and its proliferation to 

 flowers or to vegetative shoots. 



In the first place, the fruits of two species, 0. arbuscula and 0. catacantha, 

 have fruits resembling those of 0. fulgida in that they normally fail 

 to ripen. The other four species, 0. cylindrica, 0. leptocaulis, 0. rufida, 

 and 0. versicolor, apparently fail to ripen only because of some unusual 

 condition within or about them. 



Secondly, of the eight species of Opuntia just mentioned only two, 0. 

 arbuscula and 0. catacantha , seem to resemble 0. fulgida in having normally 

 persistent fruits. In the others this is the less usual thing, due in all cases 

 perhaps, as it evidently is in 0. versicolor, to some unusual cause, such as the 

 stimulus caused by Asphondylia. There are many other species also in 

 which, as was noted by Griffiths (1913), the abnormal conditions of growth 

 provided in cultivation frequently induce persistence of the fruits. 



Thirdly, the proliferation of the areoles of the ovary to flowers, while 

 apparently a normal occurrence in 0. arbuscula, 0. catacantha, and the 

 closely related 0. spinosissima, as it also is in 0. fulgida and Peireskia, is 

 a rarer phenomenon in the other four species mentioned, and in them occurs, 

 usually, if not always, under abnormal conditions. 



Finally, the proliferation of the areoles of fallen fruits to roots and shoots, 

 thus to form new plants, may apparently occur in any of the seven opuntias, 

 but not in the soft, quickly ripening fruits of Peireskia. 



