THE ANGIOSPERMAE 1547 



Moms we have already mentioned, and quite a considerable number of 

 other cases of sepal hypertrophy could be added. One of the most striking 

 is that of Dillenia reti/sa, in which the calyx becomes exceedingly fleshy 

 and the sepals, tightly wrapped around the capsule, create a ball as big 

 as a coconut. The fruit itself has little fleshy tissue and this is augmented 

 by the fleshy and edible sepal tissues, while in most other genera of the 

 Dilleniaceae the fruit itself is fleshy. 1 he petals as well as the sepals 

 may be brought into play to enclose the fruit, as in some species of Cotyledon 

 (Crassulaceae), where the corolla tube shrinks at the end of the anthesis 

 and closes around the carpels. We may here refer once more to the 

 hardened envelope around the fruit which is formed bv the base of the 

 corolla in Mirabilis and other Xyctaginaceae. 



These examples are primarily protective arrangements, but other cases 

 show assistance in dispersal. The most obvious instances are those Com- 

 positae, Valeriana, etc., in which the calyx has become a plumose attach- 

 ment or pappus, which is an important aid to wind dispersal. The styles 

 may also become hairy and act as plumes, though they may perhaps be 

 regarded as legitimately part of the fruit {Clematis). An example where 

 the calyx assists animal dispersal is that of Clerodendron fargesi, which has 

 blue berries, set oflF and made more conspicuous to fruit-eating birds by the 

 fleshy, red sepals which surround the fruits. The leaves fall before the 

 fruits are ripe and they are thus left conspicuous on the tree. Failing bird 

 dispersal the sepals act as rather primitive wings and the fruits may be 

 blown for over twenty yards (see Fig. 1389). 



Bracts are frequently retained and used either for the protection or for 

 the dispersal of the fruits, or both. The involucral bracts in some of the 

 Compositae, e.g., Arctium, Carlina, not only form protective, spiny chevaux- 

 de-frise around the fruits but may be hooked or barbed for clinging to 

 clothing or hair. The bracts in Carpinus, on the other hand, develop into 

 wings. The pedicel may also share the development of the fruit or may 

 sometimes exceed it. Anacardium occidentale, already referred to, is one 

 such case, where the swollen pedicel greatly exceeds the size of the fruit 

 itself. Another example is that of Laportea, the stinging tree of Queens- 

 land, a member of the Urticaceae (Fig. 1407). The short pedicel becomes 

 greatly swollen, pushing the single akene to one side, where it is covered 

 by a persistent and fleshy perianth segment. The swollen "berrv" is an 

 attraction to birds and aids dispersal. 



There have been suggestions that some features of the fruit and of 

 other post-fertilization developments may be influenced by the nature of 

 the pollen which caused fertilization. This is an extension of the idea of 

 Xenia, already referred to in connection with endosperm, and is called 

 Metaxenia. The effect, if it is a genuine effect, can scarcely be direct, but 

 must operate through the developing embryo and endosperm, whose 

 hormonal activity may be supposed to be affected by their genetic con- 

 stitution. The number of fertile seeds formed, and still more, the absence 

 of fertile seeds, certainly have an effect upon the character of the fruit 



