56 Phytogeogra phical Excursion in the British Isles. 
vegetation separated in a warm climate in several altitudinal belts 
converge and mix in cooler regions, because the basal vegetation 
extends northwards and at tbe same time the mountain vegetation 
descends more and more. In a continental climate the vegetation 
lines run far apart and each belt can easily be studied separately, 
while in the oceanic climate the lines merge ; for instance the alpine 
vegetation descends and mixes with montane or even with coastal 
plants. 
To get the key for the cool oceanic Killarney woods we shall 
look for comparisons in a little warmer or a little less oceanic region. 
Enjoying these beautiful Oak-holly-woods I was strongly 
reminded of similar communities I have studied in southern 
regions. What is united in Ireland is dispersed in the South in 
several belts. Let us compare the climate of Killarney with that of 
these regions I have in mind—tbe Atlantic laurineous woods , the 
“ Monte verde” or ericaceous scrub of the mountains of Tenerife , the 
Beech-pine-holly-wood and the Arbutus scrub of the mountains of 
Corsica. 
Unfortunately meteorological data of all these regions are scarce, 
as Killarney has no old meteorological station and the stations of 
the southern regions compared are nearly all located in other than 
the desired mountain belts, but we can calculate the data approxi¬ 
mately from those we have and from our own experience. 
Killarney has a January isotherm 1 2 of about 7°C and a July 
isotherm of about 15*3 n C, which gives an annual range of only 8J n C; 
frost is practically unknown: the rainfall is enormous, about 
2000 mm. per annum, and the air nearly always moist. The climate 
of the laurel woods 3 and of the heaths of Teneriffe is very similar to 
that of Killarney, only a little warmer. Having no meteorological 
station in tbe woods we must start from the basal belt. Orotava at 
100 m. has a mean temperature of 19 - 0"C, and a range of 8-7"C between 
the means of January and July (14-6°, 23’3°). The cloudy belt which 
bears the woods (between 500 and 1100 m.) and the heaths (between 
500 and 1300 m.) may have means around 13°C, a little more than 
Killarney; the extremes of monthly means about the same (8-9°C), 
perhaps a little less in the laurel wood, a little more in the heath, 
which is not quite so much centred in the cloud-belt. The relative 
humidity is very great, even the dry basal station of Orotava having 
a summer mean of 82%. The similarity is reflected in the vegetation. 
Hymenophyllum tunbridgense, Poly podium vulgare, Pteridium aqui- 
linum are all present; Hedera Helix creeps on the ground in masses. 
Arbutus Unedo is replaced by a near relative, Arbuhis canariensis ; 
instead of Ilex Aquifolium we find the more southern species Ilex 
canariensis and platyphyllos, playing the same role. Erica arborea 
and other ericaceous shrubs take the place of the less heat¬ 
demanding Calluna and Erica cinerea. The relationship is clear: 
the similarity lies in the same oceanic climate, the difference in the 
temperature. 
1 See map in R. LI. Praeger: A tourist’s flora of the west of 
Ireland, Dublin, 1909, p. 5. 
2 H. Schenck: Beitriige zur Kenntnis tier Vegetation der 
Canarischen Inseln, 1907, ami J. Harm: Handbuch der Klima- 
logie 1897, 
