Meyer also records the results of culture experiments made in the open, possibly with soredia or with thalline scraps: he obtained a growth of _Xanthoria parietina_ (on wrought iron kept well moistened), which fruited in the second year, and in five years had attained a width of 5-6 lines (about 1 cm.); _Lecanora saxicola_ growing on a moist rock facing south grew 4-7 lines in six and a half years, and bore very minute apothecia. Lindsay[897] quotes a statement that a specimen of _Lobaria pulmonaria_ had been observed to occupy the same area of a tree after the lapse of half a century. Berkeley[898] records that a plant of _Rhizocarpon geographicum_ remained in much the same condition of development during a period of twenty-five years. The latter is a slow grower and, in ordinary circumstances, it does not fruit till about fifteen years after the thallus has begun to form. Weddell[899], also commenting on the long continuance of lichens, says there are crustaceous species occupying on the rock a space that might be covered by a five-franc piece, that have taken a century to attain that size. Phillips[900] on the other hand argues against the very great age of lichens, and suggests 20 years as a sufficient time for small plants to establish themselves on hard rocks and attain full development. He had observed a small vigorous plant of _Xanthoria parietina_ that in the course of five years had extended outwards to double its original size. The centre then began to break up and the whole plant finally disappeared. Exact measurements of growth have been made by several observers. Scott Elliot[901] found that a _Pertusaria_ had increased about half a millimetre from the 1st February to the end of September. Vallot[902] kept under observation at first three then five different plants of _Parmelia saxatilis_ during a period of eight years: the yearly increase of the thallus was half a centimetre, so that specimens of twenty centimetres in breadth must have been growing from forty to fifty years. Bitter’s[903] observations on _Parmelia physodes_ agree in the main with those of Vallot: the increase of the upper lobes during the year was 3-4 mm. In a more favourable climate Heere found that _Parmelia caperata_ (Fig. 49) on a trunk of _Aesculus_ in California had grown longitudinally 1·5 cm. and transversely 1 cm. The measurements extended over a period of seven winter months, five of them being wet and therefore the most favourable season of growth. In warm regions lichens attain a much greater size than in temperate or northern countries, and growth must be more rapid.