282 BEITISH 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 Jacobcea (ragwort), Ononis arvensis 

 (rest-harrow, usually possessing spines), Hyoscyamus 

 niger (henbane), Hippophae rhamnoides (sea-buckthorn), 

 Leontodon hirtus (hawkbit), Iris fcetidissima, SoncJius 

 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), Galium verum 

 (lady's-bedstraw), Erythrcea Centaurium (centaury, usually 

 dwarf), Erodium cicutarium (stork's-bill), Euphorbia port- 

 landica, Carduus pycnocephalus (slender thistle), Carlina 

 vulgaris (car line-thistle), Myosotis collina (early forget-me- 

 not), Filago germanica (cudweed), Inula Conyza (plough- 

 man's -spikenard), etc. 



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 (sand wort), Cerastium 

 semidecandrum (small mouse-ear chick weed), Sher ardia 

 arvensis (field-madder), Plantago Coronopus, Anagallis 

 arvensis (pimpernel), Sedum anglicum, 8. acre (stone- 

 crops), Hieracium Pilosella (hawkweed). 



Finally, the association becomes closed by the develop- 

 ment of ordinary pasture-grasses, or in some parts it 



