36 THE FEUIT OF OPUNTIA FULGIDA. 



upper areoles. In the latter part of July flowers for the fourth generation 

 of the season are developing from the areoles of the tertiary ones (fig. 6). 

 These quaternary flowers probably open during August, and since the 

 blooming-season may extend into September (Lloyd, Plant World, 1917), it 

 is probable that a fifth generation of flowers may be formed in a single 

 season. I^o undoubted examples of this, however, have thus far been seen, 

 and I have not been able personally to seek them at Tucson at the proper 

 season. 



Since the fruits resulting from the four generations of flowers remain 

 attached to each other in the order of their development, it is clear that a 

 chain of fruits of at least four successive links may be developed in a single 

 season. This has been recorded by Toumey (1898), who apparently 

 believed that all chains of fruits arose in this way in a single season. He 

 definitely mentions that the " proliferous fruit hangs in pendulous clusters, 

 sometimes as many as 7 fruits in a single cluster, one growing from the other 

 in continuous succession." He regards the persistence of fruits over winter 

 and the formation of flowers from them in the succeeding spring as a rare 

 occurrence. 



The time of maturing of the seeds of the fruits of the four successive gen- 

 erations may differ considerably, since the fruits continue to grow after 

 dropping the perianth, but even the latest and smallest ones may contain 

 ripe seeds in October. All four links of the chain may commonly persist 

 attached throughout the winter and give rise to new flowers the following 

 spring. ISTot infrequently, however, the younger, quaternary fruits may 

 wither more or less during the winter and (failing to develop flowers upon 

 them in the succeeding spring) may be crowded off by the new flowers 

 developed beside them on the tertiary fruit by which they themselves are 

 borne. 



The formation of these chains of fruits of four links in a single season 

 is thus the result of the continuous uninterrupted development of the grow- 

 ing-points of certain areoles of each successive floral shoot. The structure 

 thus formed is comparable with that developed by many herbaceous plants 

 and the water-shoots of certain woody ones, in which each (or many) of the 

 axillary buds develops continuously during the season of its initiation into a 

 mature vegetative or reproductive shoot. 



Other areoles of the flower and fruit of this opuntia have quite an opposite 

 fate. In these the axial bud does not develop continuously, but (after devel- 

 oping a considerable number of trichomes and spicules and a few nectaries) 

 rests till the next growing-season, or sometimes for three or four seasons, 

 before renewing its development. 



