188 FLORA OF JERSEY. 



general character of all the islands is that of flat or sloping table- 

 lands, intersected by valleys to a greater or less extent. Nor does 

 there seem to be anything in the differences of climate, so far as 

 reliable data exist for ascertaining them, which can account for 

 such differences in the vegetation. Over a comparatively restricted 

 area, where more or less uniform conditions prevail, a much more 

 uniform flora might have been expected, and there can be little 

 doubt that at some remote period, when a far larger land surface 

 was exposed, the flora was much more uniform. Whether the 

 whole of the submerged platform was ever elevated above the 

 surface of the sea since the arrival of our present species 

 of plants it is impossible to say, but there is conclusive 

 evidence of variations of level sufficient to cause a, very great 

 increase (and also decrease) of the present land surface. The 

 islands were doubtless at some former period much more nearly 

 connected with one another and with Prance, and may well have 

 been covered with a more or less uniform vegetation of the Con- 

 tinental type. The result of subsequent oscillations would be to 

 destroy some of the rarer plants of the district by submergence, 

 and to render others still more local than they were before. As 

 the land area contracted the struggle for existence would become 

 more intense, and the preservation of rare or delicate species 

 more and more problematical, and these are just the conditions 

 under which plants would tend to become local. 



If. in addition to this, it is supposed that the South European 

 species which form the most interesting portion of the Channel 

 Islands Flora, particularly in Jersey, were subsequent arrivals, 

 the differences in the indigenous vegetation of the various islands 

 seems to be to a certain extent accounted for. 



The presence of one or two of the maritime species peculiar to 

 Guernsey may be explained by the fact that there are still salt 

 marshes in that island, while in Jersey they have been drained 

 and cultivated, and in Alderney and Sark they apparently never 

 existed. 



III. Eelation of the Channel Islands Flora to the Flora 

 OF Europe in general. 



The Channel Islands plants may be grouped as follows from the 

 point of view of their European distribution ; — = 



