282 BRITISH PLANTS 
below. All the plants possess the power of growing 
upwards when covered with sand. 
The following plants are commonly found with Psamma 
on the shifting dune, most of them being abundant on the ~ 
sheltered landward side: Agropyron junceum, Festuca 
rubra var. arenaria, Elymus arenarius (sea-lyme grass), 
Carex arenaria, Convolvulus Soldanella, Eryngium mari- 
timum, Glaucium luteum, Euphorbia Paralias (sea-spurge), 
Cynoglossum officinale (hound’s-tongue), Lycopsis arvensis 
(field-alkanet), Senecio Jacobea (ragwort), Ononis arvensis 
(rest-harrow, usually possessing spines), Hyoscyamus 
niger (henbane), Hippophaé rhamnoides (sea-buckthorn), 
Leontodon hirtus (hawkbit), Iris fetidissima, Sonchus 
oleraceus (sow-thistle). 
Grey Dunes.—As the dune becomes covered with 
vegetation its aspect changes. Instead of the dazzling 
whiteness of the shifting dune we find a more sombre tint 
prevailing, due to its living covering. On old dunes the 
most abundant plants are low-growing herbs, which form 
a rough pasture, but all stages exist between this and the 
shifting dune. Psamma is still dominant in these inter- 
mediate forms, together with many other plants of the 
shifting dune; but other plants. including many annuals, 
are abundant—e.g., Thymus Serpyllum (wild thyme), 
Lotus corniculatus (bird’s-foot trefoil), Galiwm verum 
(lady’s-bedstraw), Erythreea Centaurium (centaury, usually 
dwarf), Lrodium cicutariwm (stork’s-bill), Euphorbia port- 
landica, Carduus pycnocephalus (slender thistle), Carlina 
vulgaris (carline-thistle), Myosotis collina (early forget-me- 
not), Filago germanica (cudweed), Inula Conyza (plough- 
man’s-spikenard), ete. 
As the dune becomes more consolidated, the Psamma 
disappears, and the dominant plants are Carex arenaria 
and Festuca rubra var. arenaria. Most of the smaller 
plants in the preceding list are found also, together with 
the following : Draba verna (vernal whitlow-grass), Viola 
ericetorum, Arenaria serpyllifolia (sandwort), Cerastiwm 
semidecandrum (small mouse-ear chickweed), Sherardia 
arvensis (field-madder), Plantago Coronopus, Anagallis 
arvensis (pimpernel), Sedum anglicum, S. acre (stone- 
crops), Hieracium Pilosella (hawkweed). 
Finally, the association becomes closed by the develop- 
ment of ordinary pasture-grasses, or in some parts it 
