48 THE FRUIT OF OPUNTIA FULGIDA. 



of these are seedless. Any of the sterile, fruit-like bodies may be easily dis- 

 lodged and on moist ground their areoles may give rise to new plants. Such 

 a complete series of more or less fruit-like structures might easily give the 

 impression that these sterile propagules have arisen phylogenetically by the 

 progressive sterilization of the normal type of fruit, accompanied by an 

 increase in its povt^er of sprouting from its areoles until the sterile fruits 

 have become the chief propagative structures of this species. The plausi- 

 bility of this view we shall consider in detail later (p. 52). In the mean- 

 time, however, we must remember that the so-called fruit of these opuntias 

 is made up largely of purely vegetative elements, the internodes and the 

 areoles and their products. It is clearly for this reason that many sterile ova- 

 ries, such as in other angiosperms (where they occur commonly) would soon 

 wither and fall, may in Opuntia persist as essentially vegetative structures. 



Opuntia catacantha {0. rubescens Salm-Dyck) is a West Indian species 

 resembling 0. fulgida in certain respects more closely than any other opuntia 

 studied. It is tree-like, with very flat, paddle-shaped or scimitar-shaped 

 joints, which in the variety studied are without spines. The fruits persist 

 from one season to the next and then bear primary flowers of the latter sea- 

 son. These may bear secondary flowers and the latter form tertiary ones, 

 and thus chains of fruits consisting of at least 6 or 8 links may finally be 

 formed (fig. 90). These fruits vary in size, form, and internal structure. 

 The flowers and young fruits are slender and obconical or sometimes slightly 

 bent (fig. 90). As the fruits mature they increase considerably in size, 

 often to about twice the original length (50 to 60 mm.) and to 4 or 5 times 

 their original thickness. Mature fruits are often flattened until only half as 

 thick on one transverse axis as on the other (lY by 30 mm. for example, in 

 one sho\ATi in fig. 9). Few of the fruits have fertile seeds. 'None of those 

 dissected by the writer had good seeds, but a few ripe seeds were sent him 

 by a correspondent, the Rev. A. B. Romig, of St. Thomas, Virgin Islands. 



The seed remnants found are of various sizes up to about half-growm seeds, 

 but all are brown and withered. No definite information is available 

 regarding the ability of these fruits to sprout to new shoots, but the fact that 

 they are nearly always sterile suggests that they may serve as propagules just 

 as the fruits of 0. fulgida do. This possibility is rendered more plausible by 

 the fact that in another spiny variety of Opuntia catacantha (0. monili- 

 formis Haworth) collected on Mona Islands, near Haiti, by Dr. N". L. Brit- 

 ton, chains of short joints 1.5 by 3' cm. long are formed, which are said to 

 sprout to new plants. These are spiny and except in size are like the regular 

 vegetative joints. They are not pseudo-fruits like those described in 0. 

 leptocaulis. 



In PeiresJcia guamacho is found the most striking case of proliferation of 

 the flower that has been seen outside the genus Opuntia, and it appears the 

 more remarkable because of the large bracts and long stalks of the successive 

 flowers. In this species, as it grows in greenhouses in Washington, each 



