TYPES AND AREAS OF NATURAL DISTRIBUTIONS 199 



plants were found there too, the ranges being in fact almost as nearly 

 continuous as habitat suitability allowed. Fig. 62 illustrates this 

 point. Ideally the finding of fossil remains of the plant in question, 

 in surrounding areas where it does not now grow, will demonstrate 

 its relic nature and indicate from what period of time its local 



Fig. 63. — Map showing recent (dots) and ' fossil ' (circles) stations of the Water- 

 chestnut (Trapn uatans) in Scandinavia. (After Hulten.) 



occupation dates. This is illustrated by the present-day and ' fossil ' 

 stations of the Water-chestnut [Trapa nataiis) in Scandinavia 

 (shown in Fig. 63) and of the giant Redw^oods in the northern 

 hemisphere in general (indicated in Fig. 43). In this connection 

 it is interesting to note that whereas Trapa is now known in North 

 America onlv as an introduced weed that is apt to be aggressive, 



