It is comforting to reflect that gravestones do not last for ever, nor for very long; and in the meantime Nature is doing what she can with our ugly modern memorials, touching, softening, and tingeing them with her mosses, lichens, and with algæ--her beautiful _iolithus_. In most churchyards in southern England we see many stones stained a {195} peculiar colour, a bright rust-red, darkest in dry weather, and brightest in wet summers, often varying to pink and purple and orange; but whatever the hue or shade the effect on the grey stone, lichened or not, is always beautiful. It is not a lichen; when the staining is looked closely at nothing is seen but a roughness, a powdery appearance, on the stone's surface. It is an aerial alga of the genus _Croöleptus_, confined to the southern half of England, and most common in Hampshire, where its beautifying blush may sometimes be seen on old stone walls of churches, and old houses and ruins; but it flourishes most on gravestones, especially in moist situations. The stone must not be too hard, and must, moreover, be acted on by the weather for well-nigh half a century before the alga begins to show on it; but you will sometimes see it on an exceptionally soft stone dating no more than thirty or forty years back. On old stones it is very common, and peculiarly beautiful in wet summers. In June 1902, after many days of rain, I stood one evening at the little gate at Brockenhurst churchyard, and counted between me and the church twenty gravestones stained with the red alga, showing a richness and variety of colouring never seen before, the result of so much wet weather. For this alga, which plays so important a part in nature's softening and beautifying effect on man's work--which is mentioned in no book unless it be some purely technical treatise dealing with the lower vegetable forms--this alga, despite its aerial habit, is still in essence a water-plant: the sun and dry {196} wind burn its life out and darken it to the colour of ironstone, so that to anyone who may notice the dark stain it seems a colour of the stone itself; but when rain falls the colour freshens and brightens as if the old grey stone had miraculously been made to live. [Sidenote: Churchyard yews]