OF THE DILLENIACE^. 71 



quite simple to the mutationist, who has only to suppose 

 polyphyly to have occurred.* But more probably, Delima 

 should be united to Tetracera. 



The next genus is Tetracera, of which there are five or six 

 species in the East, and others in Africa and South America. 

 T. Icevis is found in Ceylon and Malabar, and in Java and 

 Borneo, T. Assa from Chittagong to Singapore, and in Java 

 and the Phihppines, T. Euryandra from Penang to Singapore, 

 and in the Moluccas and New Caledonia, T. macrophylla from 

 Penang to Singapore and Sumatra, T. grandis in Perak, and a 

 doubtful species in Penang. 



On the theory of mutation, as on any other tlieory, the first 

 question to arise is, How did T. Icevis get to Ceylon and 

 Malabar, as well as to the further east ? On any theory this 

 question is most easily solved if we imagine that the ancient 

 continent, on whose existence perhaps most people are now 

 agreed, Brazilia-ethiopica, had land connections, complete, 

 or nearly so, to both Ceylon and Malaya, though of course it is 

 possible, but with difficulty and with the assumption of a vast 

 amount of destruction for which we have no warrant, to explain 

 the facts of distribution with only a land connection to Ceylon. 

 But the Malayan region contains so many more genera of the 

 southern type than does Ceylon, that it is easier to explain by 

 assuming land connection to Malaya also. 



Assuming, then, that T. Icevis entered Ceylon and Malaya 

 from the south, we have only to assume that it mutated oft" 

 T. Assa and T. Euryandra, or one of these (which then gave 

 rise to the other) at an early period, which would allow them 

 also to spread widely , while one of them gave rise to the other 

 three species. The general morphology of Tetracera sliows 

 that it is a comparatively primitive genus, and this would 

 "account for its species being in general comparatively wide- 

 spread, as well as for other species being found also in Africa 

 and in South America. 



The third genus is Acrotrema ; there are seven species 

 in Ceylon, besides A. costatum from Moulmein to Singapore, 

 and A. Arnottianum in Malabar and Travancore. The land 



* Willis, .Morphology and Ecology of the Podostemacese. Ann. 

 Perad., I., 1902. p. 44(i. 



