THE FRUIT OF OPUNTIA FULGIDA. 49 



flower usually bears 4 bracts and each of these has a secondary flower in its 

 axil. The stalks of a secondary flower may get to be a centimeter long or 

 more and this gives the flower-cluster quite a different appearance from that 

 of an opuntia, though its general plan is the same (figs. 92, 93). One or 

 two, rarely more, of the flowers in such a group may develop fruits (cf., 

 Delavaud, 1858). Each globular, fleshy fruit bears a well-defined areole 

 above each bract-scar and usually contains from one to several large, flat 

 seeds. These seeds germinate readily, but all attempts to induce the areoles 

 of a detached, unripened fruit to proliferate to a shoot failed. No case of 

 the vegetative proliferation of the areole of a fruit was observed. In a 

 similar species of Peireskia growing at Chico, a single parent fruit some- 

 times bore 5 secondary fruits and the basal secondary ones not uncommonly 

 bore in turn tertiary fruits ; that is, three generations of fruits were formed 

 in a single season. 



In the second series of species mentioned on page 47 the attached friiit 

 sometimes proliferates to form vegetative joints as well as to give rise to 

 flower buds. All but one of these opuntias resemble 0. fulgida in that they 

 form these vegetative shoots only rarely. Thus, in the flat-jointed species, 

 Opuntia rufida, from Doctor Rose's collection in Washington, in 0. spinosis- 

 sima from Jamaica, and in 0. discata, studied in the field at Tucson, the 

 development of vegetative shoots from attached fruits occurred very infre- 

 quently (fig. 94). Hildebrandt (1888, p. 112) has reported such a case in a 

 flat-jointed Opuntia gro\\dng in Freiburg. He attributed this imusual 

 behavior to exceptionally good nutrition of the cultivated specimens. Pro- 

 liferation of the fruits I foimd not at all uncommon in a number of the 

 above-mentioned opuntias, and of other flat opuntias growing in the collec- 

 tion of Doctor Griffiths, at Chico, California {cf. Griffiths, 1913). In the 

 cylindrical species, 0. versicolor, the occurrence of such a proliferation of 

 the attached fruit to vegetative joints is relatively very rare, only 3 or 4 cases 

 being seen in hundreds of plants examined. In two at least of the three 

 cases of this tjq^e observed the proliferating fruit was evidently a gall fruit 

 (fig. 85 ) . This fact of itself proves that these gall fruits do not always drop 

 off during the second spring. It is doubtful, however, if they are capable, 

 except in the rarest instances, of holding on long enough to make their vegeta- 

 tive offshoots an important part of the branch system. The irregularity in 

 branching, usually resulting from proliferation of a gall fruit to a branch, 

 should make this phenomenon discoverable several years after its occurrence 

 (figs. 85, 86). No certain cases could be found, however, that indicated 

 clearly the persistence of such a fruit-borne branch for more than a year or 

 two. This sort of proliferation is practically identical with that occurring 

 so rarely in Opuntia fulgida, except that in the latter the proliferating fruit 

 is in other res])ects often a normal one. 



On the contrary, in the round-jointed Opuntia arhuscula, the proliferation 

 of attached fruits to form vegetative shoots is, under some conditions at least, 

 4 



