DISTRIBUTION OF SPHAGNUM AND CAREX 345 



sufficient here to restate our present position that in its limited con- 

 nections Africa offers a great contrast with South America and 

 Australia, which are in both cases linked by a number of species with 

 the great land-masses of the north. Africa, it would seem, is a lonely 

 continent as far as the Peat-mosses are concerned. 



The outside Connections of the African Carices. — Coming 

 to the African Carices, we find that although the proportion of those 

 that extend beyond the limits of the continent, as here defined, is 

 about the same as in Sphagnum, the genus is brought by the con- 

 nections of its outside species more in touch with the rest of the 

 world. The seven species concerned, Carex divisa, vulpina, cernua, 

 externa, cederi, acutiformis, boryana, are, with the exception of the last, 

 wide-ranging Eurasian species that in one or two cases include 

 Australia and sometimes even North and South America in their 

 range. The only special connection is that of C. boryana, which 

 extends merely to Madagascar and the Mascarene Islands. 



But in one respect the African Carices repeat in a remarkable way 

 the behaviour of the Peat-mosses. In view of its isolation one would 

 have expected Africa to be the home of the older types of these 

 genera. But the contrary seems to be the case. Just as with 

 Sphagnum nearly 60 per cent, of the African species belong, as 

 already shown, to the largest and most vigorous subsection of the 

 genus, so with Carex more than half of the species belong to the 

 youngest, most vigorous, and most generally distributed of all the 

 four subgenera, namely, Eucarex, a subgenus holding two-thirds of 

 all the known species of Carex, 800 in all. It is remarkable that 

 Primocarex, the oldest subgenus, almost fails in Africa. It would 

 thus seem that the invasion of Africa by the Carices and the Peat- 

 mosses took place during the later stages in the history of the two 

 genera, and that the occupation of the continent has been followed 

 by a period of isolation extending to our own times. This similarity 

 in behaviour on the part of two groups of plants so divergent in 

 character is a fact of importance. 



In the case of Carex the limitation of the species to the continent 

 often seems to be unaccountably abrupt. Thus, there are four 

 species (C. echinochloe, boryana, longipedunculata, and simensis, 

 that are evidently distributed over the highlands of tropical Africa 

 from the Cameroons to Abyssinia and have been found on Ruwenzori 

 and Kilimanjaro at altitudes of 7000 to 10,000 feet. Though they 

 extend practically to the eastern and western limits of the continent 

 only one of them, C. boryana, passes beyond them ; but it does not 

 travel farther than Madagascar and the Mascarene Islands. In two 

 of the islands just named, Bourbon and Mauritius, this species meets 

 C. brunnea, one of the most widely distributed of the Carices in warm 

 latitudes. Ranging far and wide over Asia, it reaches Australia 

 across the Malayan region, and finally establishes itself on the Hawaiian 

 Islands in mid-Pacific. Yet there is no record of C. brunnea from the 

 African mainland. There must be some important principle in- 

 volved in the circumstance that Carices find it so difficult to enter 

 the African continent, and so difficult, when there, to leave it. 



Sources of South African Carices and Peat-mosses. — An 



