128 
The Irish Naturalist, 
May, 
have been printed on the " one-inch " Ordnance maps, and the result 
is so satisfactory in clearness and detail that it is to be hoped the 
method will be followed in all future vegetation maps. The colour 
scheme has been adopted by the authors after careful consideration, 
and on grounds stated (p. 177). It differs to some extent from that used 
by other workers, and will probably be criticised on this account. It 
must be borne in mind, however, that the earlier colour-schemes were 
experimental, and that a standard scheme can only be prepared after 
the vegetation of the British Isles is better known than it is. The 
vegetation maps published up till now fall into two groups— those pub- 
lished on the "2 miles to an inch" maps {1:126720), and those on 
the " one inch to a mile " (i : 63360). The Dublin District belongs to 
the "one inch" group, along with the maps of Westmoreland {Geo- 
graphical Jounial, March and Sept., 1904). Two different systems are 
represented on these maps : the "solid," where each association has a 
distinct colour (Dublin map), and the " dot and dash '* system, where a 
few ground colours are used, and differences are indicated by dotting 
and cross-hatching. The " solid system " is certainly the most distinct 
on a map, but the other system aims at grouping the associations- 
Comparing the " one-inch " maps with the half-inch," it is evident that 
the former allows of much greater detail being shown ; thus, the asso- 
ciations designated as Pteris, Juncus, and Ulex in the Dublin map are 
too small to be separately coloured in a "half-inch" map, and are 
there included under some other colour, although described as separate 
associations in the text. It is easy to criticise, but it is no easy task to 
fix on a definite colour scheme. The Dublin map has many points of 
value which will aid in fixing such a system. 
The Zones of Vegetation. — The district south of Dublin has not many 
features of interest as a woodland area, and in itself is not large enough 
to allow of much discussion regarding the distribution of trees. Com- 
pared with England and Scotland, we find a general agreement. Oak 
forest in the main valleys gives way to a Birch scrub in the uplands, 
with remains of Birch in the peat up to 1,700 feet. The existing plan- 
tations of Scots Pine are found on the moorland edge, but the existence 
of an earlier forest is indicated by stems found in the peat up to 1,250 
feet. The occurrence of Ash with a Hazel scrub on the Mountain Lime- 
stone recalls what has been observed in the valleys of this geological 
formation in Yorkshire. 
The Hill Pasture forms a zone on the upper limits of cultivation. In 
the earlier "half-inch" maps this was represented by one colour, but 
in the Dublin District map it is broken up into Pteris association, 
Nardus Heath, and two Ulex associations The main interest centres 
round the Bracken and Gorse associations, none of which have been so 
fully dealt with in any of the preceding British papers, but' the limited 
extent of the Nardus Heath will be noted by workers in areas where 
this is a prominent association. The authors note a strong competition 
between Bracken and Gorse in which the Bracken is the aggressor. 
