THE FRUIT OF OPUNTIA FTJLGIDA. 37 



PROLIFERATION OF PERSISTENT ATTACHED FRUITS. 



While certain of the upper areoles of a flower may, as we have seen, 

 develop at once into secondary flowers which open soon after the primary 

 one, other areoles of the same or another flower may practically cease growth 

 with the opening of the flower and persist over one or more winters as resting 

 buds. These buds, retaining their capacity for further development, may 

 give rise, in the succeeding or a later spring, to the primary flowers of 

 that season (fig. 4, 7c). Such flowers may arise from any of the 4 or 5 

 younger fruits of a chain (fig. 4). 



The development of these flowers, arising from resting buds of persistent 

 fruits, is identical with that of flowers arising from the areoles of flower- 

 buds, and the fruits formed in the two cases can not be distinguished. The 

 flowers arising from fruits, just as those from the areoles of unopened 

 flowers, may give rise in turn to buds of secondary flowers, and these to ter- 

 tiary and perhaps quatemaiy ones in the same season. The repetition of 

 this process of budding out flowers from fruits and then flower from flower 

 several times each season, when repeated season after season, results finally 

 in the formation of fruit clusters of great size. Clusters of 20 to 30 fruits 

 are common, and clusters of 100 or more fruits of all ages suspended from a 

 single parent fruit are not rare (figs. 2, 3). Some of the longer chains may 

 embody 12 or 14 generations of fruits in a single chain (fig. YY). Since, as 

 we have seen, certain of the links added in any one season may wither and 

 fall off, it is evident that a chain of 12 generations of fruits does not repre- 

 sent merely the growth of three seasons, 4 fruits per season, but may repre- 

 sent the product of five or six seasons ; in fact, the size and appearance of 

 some of the basal fruits of these clusters indicates an age of more than 6 

 years. The records of the effect of exceptionally cold winters on the plants at 

 Tucson show that it must often take many seasons to build up a chain of 12 

 or 14 links. Thus, in the winter of 1912-13 there was an exceptionally hard 

 freeze, soon after which great numbers of the younger persisting fruits fell 

 off the trees, so that chains of more than 3 or 4 links were hard to find'. 

 Such a periodic shortening of the chains, even if it occurred but once in 

 three or four winters, would increase considerably the number of summers 

 necessary to produce chains of fruits of the total length of the longer chains 

 found. 



The ease with which these fruits may be set free from the plant will be 

 the more readily realized when we note the very slender stalks by which the 

 heavy fruits are attached (figs. 25, 26). These stalks also, especially in the 

 younger fruits, have little lignified tissue. Jarring of the tree by wind or 

 by browsing cattle, which eat many of the fruits in dry seasons, may shake 

 off numbers of fruits that are often found strewn thickly beneath larger 

 plants. The stalks of the older fruits, on the contrary, become steadily 

 thicker and stronger, and the upper ones are thereby enabled to hold the 

 heavy clusters that hang from them. 



