228 PLANTS, SEEDS, AND CURRENTS 



ward it intrudes into the area of Sccevola Kcenigii, attaining its limits 

 in this direction in Southern India, Ceylon, and Mauritius; and at 

 times both species are recorded from the same limited area, as in 

 Mauritius. 



Generally speaking, the domain of Sccevola Kcenigii begins where 

 that of Sc. Plumieri ends. It is not recorded either from the Pacific 

 side of America, or from the East Coast of Africa, which in a general 

 sense represent the limits of the area appropriated by its sister species. 

 But between those continental coasts it ranges through the tropical 

 zone, and sometimes extends beyond. Thus we find it on the 

 beaches of the Pacific islands from Rarotonga to Hawaii and from 

 New Caledonia to Liu-Kiu, in the northern part of Australia, in 

 New Guinea and throughout Malaya, in South-eastern Asia, and in 

 the islands of the Indian Ocean. It finally reaches its westward 

 limits on the Malabar coast, in the Seychelles, and in Madagascar, 

 but apparently not reaching the East Coast of Africa. 



It has already been said that these two interesting species of 

 Sccevola, in dividing the coasts of the warm regions of the globe 

 between them, raise the same issues as those presented by Carapa, 

 Rhizophora, and Tournefortia, where in each case two sister species 

 similarly divide the world; but there are important differences. 

 Although one of the two littoral plants of each genus is widely 

 spread in the New World, it is confined there in the case of Tourne- 

 fortia. With Carapa and Rhizophora the American shore plant 

 extends to the African West Coast, but is not found on the east side 

 of that continent; whilst the American Rhizophora meets the 

 Asiatic species in the Pacific islands, as in Fiji. 



Before going further something may be said of the genus to which 

 the two littoral species of Sccevola, which are here compared, belong. 

 Of eighty- three species recognised by Krause, fifty-eight, or 70 per 

 cent., are confined to the Australian region. The rest are nearly 

 equally divided between the Malayan region (including New Guinea) 

 and the Pacific islands, excepting the two shore species with which 

 we are specially concerned. 



Looking at the facts of distribution relating to the Goodeniaceae 

 given in this monograph, one becomes conscious, as regards Sccevola, 

 that one is dealing with a modification of a geographical type rather 

 than with a genus as usually understood, since it is pointed out by 

 Krause (p. 14) that of the thirteen genera in the family ten are confined 

 to Australia and Tasmania, and that of the total of 291 species only 

 twenty- seven, or 9 per cent., are found outside this region, the bulk 

 of the species being restricted to the western half of Australia. It 

 is of importance to note that of these twenty-seven species all but 

 two species belong to Sc&vola, a very significant indication that 

 this genus has been especially favoured in its means of dispersal. 



Sccevola, therefore, is not only in the main an Australian genus, but 

 it belongs to a family that is also chiefly Australian. It is a member 

 of a family that thrives where the physical conditions often deter- 

 mine the xerophilous habit in plants, and, as I have before observed, 

 this habit is the first requisite for a littoral station. It is, therefore, 

 in this connection of special interest to refer to the remark of Krause 



