THE FRUIT OF OPUNTIA FULGIDA. 47 



PROLIFERATION OF THE FLOWER OR FRUIT 

 IN ALLIED SPECIES. 



The proliferation of the ovarian wall, either in flower or fruit, has been 

 noted in a number of other opimtias, and in at least one other genus, by 

 Engehnaun (1887), Hildebrandt (1888), and a number of more recent 

 workers. (See also, Penzig, 1890, p. 507). Associated with this prolif- 

 eration in certain cases we find a persistence of the fruits for one or more 

 years after maturing. The areoles of the attached fruits of some of these 

 species are known to form flowers only. The attached fruits of others, on 

 the contrary, may develop not only new flowers and fruits, but, under certain 

 conditions, give rise to vegetative shoots also. Of the first type are Opuntia 

 cylindnca, 0. leptocaulis, 0. catacantha, and Peireskia guamacho Rose. 

 Of the second sort are Opuntia rufida, 0. spinosissima , 0. discata, 0. versi- 

 color, and 0. arbuscula. 



Opuntia cylindrica, growing under cultivation but out of doors at Del 

 Monte, California, frequently formed flowers by proliferation from the per- 

 sistent fruits of the previous season (fig. 88). This same species also fur- 

 nished striking examples of the development of first a vegetative joint and 

 then a fruit by the uninterrupted activity of the same growing-point ; that is, 

 the joint and fruit are separated by only a very slight constriction, as was 

 noted in speaking of Opuntia fulgida (cf. figs. 7c^ 88). From the plants of 

 0. cylindrica observed there is no evidence that the primary flowers ever give 

 rise to buds of secondary ones before they are open. 



Opuntia toumeyi, growing near Tucson, may occasionally form secondary 

 flowers close to the base of the primary ones, which open soon after the latter. 



Opuntia leptocaulis is a slender Arizona species, growing along with 0. 

 fulgida, in which fruits may persist unripened or half-ripened and then 

 bud out new flowers in the succeeding season (fig. 89, a, h, c). These pri- 

 mary fruits may persist for a year and a half and the secondary ones may 

 ripen, but tertiary fruits are rarely formed. The propagative structures 

 here show a very closely graded series of intenuediatc forms between the 

 typical fruit and the vegetative joint, a series far more complete than can 

 usually be found on 0. fulgida or any other near Tucson. One plant of 0. 

 leptocaulis seen at Chico in August bore numerous slender vegetative 

 joints on persistent fruits of the same season and also of the preceding season. 



The graded series of propagative structures above mentioned contains 

 typical obovate fruits, with definite perianth-scars, evidently fonned by nor- 

 mally opened flowers. Other fruits are twice as long, but still show the scar 

 of a normal perianth. Then there are joints of various lengihs, of wliich 

 some bear small or very small perianth-scars while others have no scars at 

 all, and yet all of them look very fruit-like in other external aspects. There, 

 are also many slender joints having no perianth-scars, yet closely resembling 

 the more slender sterile fruits that do have them, l^one of these various 

 structures except the shorter, obovoid ones may contain seeds, and some even 



