INTRODUCTION. 
IX 
nature of the localities, exercise such an influence over vege- 
tation, that no definite limits can be fixed for the inflores- 
cence of various species. For example, Cochlearia green - 
landica is sometimes found in flower on the coast as early as 
April, and in other seasons not till June; while on the 
mountains its blossoms rarely appear before July, and in late 
seasons, not till August. 
There is the same difficulty in respect to the Zonal range 
of vegetation. Silene maritima, Statice Armenia , Lychnis 
diurna, Cardamine pratensis and hirsuta, Bryum trichodes, 
Weissia niyrita, Fegetella kemispherica, and several others, 
might be placed either in the maritime or subalpine zone ; 
and Lychnis alpina, although found indigenous only on the 
highest ground in the county, flourishes luxuriantly in our 
gardens a little above the sea-level. 
Under these circumstances, it was deemed most prudent 
to leave to those, who possess greater experience, leisure and 
opportunity, with “ all appliances and means to boot,” to 
ascertain, if possible, or even to approximate, the latitudinal 
and altitudinal limits of the respective species; and merely 
to state such facts in connection with the subject as might, 
with tolerable confidence, be relied upon. There is no 
doubt a limit to every species of plant, as respects latitude, 
longitude, and altitude ; but this is so much under the con- 
trol of local circumstances, that no general rule can apply to 
every locality. 
The comparative numbers of British and Forfarshire ge- 
nera, species, and varieties, are given under each natural 
order; and those of the species and varieties are repeated 
under each genus ; so that, at a glance, may be seen what 
proportion our county Flora bears to that of Britain. To 
render this comparison more complete, a table is given at the 
end of the book (p. 299) including all the British natural 
orders, in which those absent from Forfarshire are distin- 
guished by being printed in italics. 
The county of Forfar, or Angus, is situated between 56° 27' 
and 56° 56' N. lat., and between 2° 28' and 3° 22' W. long. 
