CH. XI] B. MORPHOLOGICAL 123 



(incidentally, therefore, the berry fruit must have been acquired 

 independently of that of Tamus) ; while Dioscorea, with 600 species 

 and a capsular fruit, is in all warm countries. Such cases are 

 common in many different instances of various fruits. There is no 

 evidence to prove that advantage is gained by the possession of a 

 berry. In fact, as was pointed out in Age and Area, p. 21, nothing 

 in the distribution of plants would lead any one to suppose that 

 the " mechanisms for dispersal " have produced for the plants that 

 possess them any wider dispersal than usual. Tithonia, with no 

 pappus, and with mainly vegetative reproduction, spread as 

 widely as, and not much more slowly than, the bird-carried 

 Lantana in Cevlon, to which both were introductions. 



The berry may occur in the whole or part of a family, in a few 

 genera, in one, or in part of one. Considering the wide taxonomic 

 separation of many of the berry families, it is clear that it is very 

 improbable that all derived it from the same ancestor, unless the 

 character could remain dormant for immense periods of time and 

 change. It would rather seem to be one that is easily acquired, 

 perhaps through some kind of kaleidoscopic change in the assort- 

 ment of genes. 



To explain why the berry is more common than the drupe, 

 which is equally well adapted to transport by birds or animals, 

 the selectionists have to bring up one of their many supple- 

 mentary hypotheses, this time a "tendency" to vary rather in 

 the direction of berry than of drupe, or again an admission that 

 morphological facts weigh more in evolution than does selection. 

 Presumablv there is a still greater tendencv to varv in the 

 direction of the capsule, the least "efficient" fruit of the three. 

 And whence did the tendencv come, unless it were handed down 

 from a common ancestor in each group, for whole families like 

 Epacridaceae show a tendency towards the drupe, while their 

 close relatives Ericaceae show a tendency chiefly towards the 

 berry, but sometimes towards the drupe? Rhamnaceae have a 

 dry fruit or a drupe, their close relatives the Vitaceae a berry. In 

 the genus Chironia (Gentianaceae), mainly African, a small 

 group of species in South Africa and Madagascar have a berry, 

 the rest capsules. Why are there no berries in most of the generic 

 area? This geographical localisation of structural features is 

 common ; e.g. in Styrax, the first genus to come to hand, most of 

 the species have sixteen to twenty-four ovules, but there are 

 some with three to five in Cuba and in Peru. It is a matter of 

 great difficulty, if not impossibility, to explain such cases by 



