68 INTRODUCTION. 
range will partly compensate for the brevity, more especially in 
reference to the lower limits which are seldom given. With com- 
paratively few exceptions, less than a hundred, all the plants 
treated occur at or near the coast-level in some part of the island ; 
the greater, number of them being found on the low open country 
of the southern counties, away from hills of any considerable 
elevation. Many of these also ascend the acclivities of the 
northern and western mountains, though to widely unequal 
heights, as previously explained on pages 11 to 13. All the 
species indicated as occurring in the first zone, are found at a 
trifling altitude in South Britain, and far the greater number of 
them at or near the coast-level,—say, between the level of the sea 
and one hundred yards above it; and thus “zone 1” is almost 
equivalent with the words “ descending nearly or quite to the 
coast-level in latitude 50—53.” Of those which commence in the 
second zone, also, nearly all descend to the like low level in Mid 
Britain ; though of course not so low in South Britain, “otherwise 
they would have been assigned to the first zone. Some few of 
those indicated to find their lowest climatal limit in the third 
zone, have not been recorded so low as the coast-level anywhere in 
Britain ; for instance Luzula spicata and Sibbaldia procumbens. 
But most of them do descend nearly or quite to the coast-level in 
North Britain, although rarely found so low even there. Thus, for 
the most part, it will suffice to give indications of upper limits only ; 
making occasional exceptions to this rule, when some indications 
of lower limits may seem specially desirable. The figures (which 
denote the highest observed localities in yards of three English 
feet) are primarily divided into three sets, respectively belonging to 
North Britain, to Mid Britain, and to South Britain; the last 
division being seldom mentioned, and then usually by naming 
instead some subordinate province or county, as North Wales or 
Devon. For those plants which rise to the greatest heights, only 
North Britain will need to be mentioned; the hills of that division 
greatly exceeding those of Mid Britain in altitude. The first 
numeral figure will indicate the highest station noted, whether by 
measurement or by estimation ; other heights being added thereto, 
