TRAP-FLORA OF RENFREWSHIRE, ”; 
6. Rosaceous stage—About this time there appear in the whin 
and broom thickets the first invaders of the sixth or Rosacez 
stage. 
Roses, hawthorn and rowan are the commonest; then 
brambles and sloes (latter not so common). Amongst them, 
foxgloves and, occasionally, ashes show that if left alone a wood 
might develop. Woods, in fact, do grow luxuriantly on those 
faces which are too steep and broken for the plough, as may be 
seen everywhere in Renfrewshire. Nor are they necessarily of any 
one kind. A beautiful example occurs near Kilmacolm, above 
the Gryffe, on the steep slope. Pines also grow on them well 
(with bracken); so also do oaks and mixed deciduous woods, 
with a luxuriant woodland undergrowth; beech occurs when 
planted, and has often a homogeneous Ho/cus wood-floor. 
Altitude has nothing to do with this distribution. I drew out 
a list of characteristic plants noticed in twenty typical localities 
(see page 10), and found that there were very few, comparatively, 
which could be held characteristic of any altitude. 
It is true that the “Summit” or Vaccinium flora from 1,500 to 
1,700 feet (Robber Craigs, Misty Law, Hill of Stake, East Girt 
Hill, Boxlaw and High Corby Knowes) differs in the presence of 
the Lycopodias and /uncus sguarrosus and the absence of many 
plants common below; but then I have no doubt that we could 
find all the others if the highest hills were four or five thousand 
feet. It is not altitude in feet above sea level, but exposure to 
wind, snow and heat, that keeps out these lower plants. 
On the Alps, five species, according to Vaccari, reach 4,200 
metres, z.¢., 13,000 feet. Lichens occur elsewhere at 6,010 metres, 
and Saussurea tridactyla at 19,000 feet. Even the beech may 
ascend higher up the mountains than the oak. It is not mere 
altitude, but the conditions of rain and climate that affect this 
flora. 
The “summit flora” represents an arrested development. 
In that rainy and exposed situation, after the Vaccinium (3), 
sphagnum appears, and covers or chokes out all plants which are 
unable to adapt themselves to the new conditions. 
Cottongrass, LZvica tetralix and £. cinerea and Scirpus 
cespitosus would be the next stage (with Ca//una and lichens or 
blaeberry growing on any dry patches). 
