6 THE FRUIT OF OPUNTIA FULGIDA. 



formed in the embryo sac; secondly, there follows soon after pollination, 

 which is usually succeeded by fertilization, a period of active vegetative 

 growth of the ovary and often of other parts which are to enter into the 

 make-up of the fruit. While the fruit is thus growing to its mature size 

 the seeds are also taking on their characteristic form and size. Thirdly, 

 accompanying or immediately succeeding the final maturing of the seeds, a 

 process of rij^ening occurs in the fruit. During this ripening process the 

 outer tissues, the mesocarp and epicarp of the fruit, may soften to form a 

 juicy pulp. In this case the starches, distasteful glucosides, acids, tannins, 

 alkaloids, etc., which are often present in the cells of this pulp in the green 

 fruit, are transformed into the sugars, mild acids, and other tasteful flavors, 

 and often also into brightly colored glucosides that make the fruits attractive 

 to animals. While these changes are taking place in the outer layers of the 

 fruit the inner layer, the endocarp, may harden to form the firm stone that 

 j)rotects the seed when it is eaten by animals. In other types of fruits, as in 

 pods and capsules, the ripening process involves a drying out and hardening 

 of all the tissues of the fruit. 



Ripening of the fruit is usually followed, often very promptly, by ita 

 separation from the plant or by its dehiscence and the discharge of its seeds. 

 Either of these two fates of the fruit involves the more or less immediate 

 death of its tissues, aside from the seeds. In a few fniits, such as that of 

 palms like the coconut or the pomes of the Rosacese, certain tissues of the 

 fruit may remain alive for some weeks or months after separation from the 

 parent plant. The growth occurring in these cases is, however, compara- 

 tively slight and it does not give rise to new buds or new plants. 



In the cases of certain opuntias, chiefly cylindropuntias, the fruits differ 

 from the usual type characterized above in several very remarkable particu- 

 lars. In the first place the fruits do not ripen with the maturing of the 

 seeds, but continue to grow actively without undergoing the usual softening 

 and change of color and of chemical composition so characteristic of the 

 ripening process of most fleshy fruits. Secondly, the fniits of 0. fulgida 

 are not shed from the plant when the seeds are ripe, but usually remain 

 firmly attached and growing, year after year. Thirdly, these attached 

 fruits (or even the unopened flowers), may, in situ,, give rise from their 

 axillary buds to from one to ten secondary flowers and fruits. A few weeks 

 later these secondary flowers may give rise in the same way to tertiary ones 

 and these in turn to quaternary ones. Thus, three or four generations of 

 flowers and fruits may be produced, all in a single blooming season of three 

 or four months. Fourthly, if the fruits become separated from the plant 

 and fall on moist soil, the same axillary buds which in the attached fruits 

 would form nothing but flowers will, in the fallen fruits, give rise to 

 vegetative shoots and roots and to these only. Finally, the embryos of the 

 ripe seeds, inclosed in the persistent, attached fruits, retain their power of 

 germination for many years. 



