122 TEST CASES [ch. xi 



selection, and that natural selection can do nothing to explain 

 staminal morphology. The phenomena shown can only, at 

 present, be explained by the supposition of sudden mutation, 

 causing, for example, the loss (or gain) of five stamens, or the 

 formation of a new method of dehiscence, etc. 



TEST CASE XIV. THE BERRY FRUIT 



The berry, as seen in the gooseberry or grape, is a well-marked 

 and distinct type of fruit, the only hard part being the seeds, 

 though there is a skin upon the outside. In the drupe, as seen in 

 the cherry or the plum, the innermost layer of the fruit wall is 

 hard, and the seed (kernel) inside this is usually soft. 



There are berries in about a third of existing families, and as 

 these contain more than half the total of genera, they are upon 

 the large (old) side. But only a portion of their genera have 

 berries. Berries occur all through the flowering plants, including, 

 for example, the Araceae, Bromeliaceae, Rafflesiaceae, Annona- 

 ceae, Vitaceae, Myrtaceae, Ericaceae, Solanaceae, and Cam- 

 panulaceae. 



The fleshy fruits have always been a standby of the supporters 

 of selection, who of course had to find adaptational reasons for 

 phenomena, and supposed these fruits to be adaptations for dis- 

 persal of the seed. But if the seed be carried far, it will likely be 

 dropped into another association of plants, where the competi- 

 tion will be equally severe, and the conditions probably different, 

 so that it will be, if anything, at a disadvantage. One rarely 

 finds another plant growing in an association to which it is 

 foreign. 



The berry and the capsule go together very much in related 

 groups, but the capsule is much commoner, though it shows no 

 adaptational advantage; the seed may be shaken out in a wind, 

 but that is all. Some berried families, like Annonaceae, are com- 

 mon and widespread, but so are capsular families like the 

 Caryophyllaceae. There is no evidence to prove any adaptational 

 value in a berr}^ An instance which was sometimes brought up 

 was the family Taccaceae, where Tacca, with a berry, is wide- 

 spread through the tropics, and Schizocapsa, with a capsule, the 

 only other genus, is confined to Siam and South China. But in 

 Dioscoreaceae, one berried genus, Tamus, is confined to Europe 

 and the Mediterranean, and has only two species; the other, 

 Peter mannia, with one species, occurs in New South Wales 



