SOU'J'-II AFKLCAN llKl'Al'IC.'E. 433 



iiianent or general nature, rather than varieties, and it is quite 

 probable that some local so-called ciideinic species come under 

 that head. 



As some of the South African species are known to also occur 

 in India, China, Japan, Java, Australia, North, South, and 

 Central America, West Indies, and many oceanic islands, as 

 well as in Europe and in other parts of Africa, there would be 

 little reason for surprise if others, now regarded as South 

 African only, prove eventually, when better known to a larger 

 circle, to be also represented elsewhere ; nor is there any reason 

 for surprise if many further foreign species be still found in 

 South Africa, where so man\- different climatic conditions 

 occur. 



And it must be rememl)ered tb.at in many cases a herbarium 

 expert deals with a specimen, or even a scrap, rather tham a 

 species, and would give a different verdict if he could combine 

 abundant held work, in many countries, with his microscopic 

 study. It is evident that the main groups and even the larger 

 genera are practically cosmopolitan, a proof either that these 

 types are very primitive or that their trans-oceanic distribution 

 is more easily accomplished than is that of Phanerogams. How 

 that distribution occurs has not been proved, but it seems prob- 

 able that the spiral elaters may be at least one factor, since the 

 spores often adhere to the elater, which may act as a float in 

 long-distance wind currents. If this be so, it indicates extra- 

 oidinary endurance on the part of the spore — an endurance also 

 exhibited against extreme cold in arctic and antarctic regions, 

 and against extreme drought in desert rc,:^ions — and it also 

 points to a use for the papilla? which cover the spores of many 

 species. 



It is believed that the Hepticie are a very primitive group, 

 but if the world-wide distribution dates back to remote ages, 

 under different geographical and climatic conditions, then one 

 would expect more ])ronounced local specific and even generic 

 variation than actually occurs, were it not that the environment 

 has remained more or less the same, being a water environment. 



A good many species have identical characters in all parts 

 of the world : are these fixed types which have remained un- 

 broken through countless ages, or are they more recent types, 

 possessed of long endurance in the spore condition and well- 

 developed though still undetected or unproved powers of trans- 

 portation ? 



Strong arguments may be ])roduced in favour of either 

 view ; for the foriuer is the fact that the same cosmopolitan 

 character is seen among the green fresh-water Alga;, and these 

 could not have been distril)uted by wind or even by salt water ; 

 for the latter view is the fact tb.at some of these world-wide 

 species are ubiquitous where conditions are favourable, occurring 

 even in remote oceanic islands and in spots far distant from 

 the nearest locality suitable for and inhabited by the same class 



c 



