Mar. 1911.] BOTANICAL SOCIETY OF EDINBURGH 159 
Anthoranthum odoratum is frequently a sub-dominant. 
Many varieties of the association might be distinguished, 
for it has a wide range. 
One of the commonest forms, characteristic of rather 
poor pasture, has little or no Cynosurus and an abundance 
of Leontodon autumnale. On wetter ground this Leontodon 
variety contains C. panicea, ete., as well, and becomes “poor 
wet pasture.” Rich pasture may, on the other hand, have 
little Agrostis and Leontodon—the Cynoswrus variety. 
On steep grassy banks the taller and more varied assem- 
blage of plants described previously may usually be regarded 
as a third variety of the Cynosurus-Agrostis association. 
The subordinate plants in this association have been 
largely enumerated in speaking of the formation as a 
whole. Others are mentioned in the examples below. On 
certain soils a thick springy turf of Hypnec obscures 
the grasses in winter time. 
2. Pow pratensis association.—In the richest old pasture, 
which is also sheltered from the biting spring winds, a more 
southern type of pasture may occur than is usual in Orkney. 
Pou pratensis, being usually abundant, may give its name 
to the association, but over small areas various grasses may 
dominate. Lolium perenne, Agrostis, Holeus, and Cyno- 
surus are abundant, as well as Poa, while Alopecurus 
pratensis and Phleum pratense reproduce themselves 
naturally in such quarters. Rye-grass, Timothy, and Fox- 
tail are not indigenous in Orkney. 
The accessory plants with bright flowers ave also different 
in this association from what is found in the preceding one. 
Ranwneulus acris takes the place of Leontodon, and, 
along with Bellis, gives colour to the field. 
Trifolium repens is very abundant in this, as in richer 
forms of the Cynosurus-Agrostis association. 
Sub-Formations IIT. and IV. 
“Sand Pasture” and “Maritime Pasture,’ as already 
stated, are included in another cecological section. 
The Successions. 
A study of the successive changes which take place in 
the conversion of natural formations into grassland, and 
TRANS. BOT. SOC, EDIN. VOL. XXIV. diy 
