BOTANY as the field ragwort or mountain fleawort {Senecio campestris) and the cat's- foot {Antemiaria dioica) require. The process appears to be complete so far as exterminating the former is concerned, while the latter, with the spotted cat's-ear [Hypochceris maculata), only linger in a solitary locality. It must also be borne in mind that with the growth of the richer herb- age of the grasses I have named, there is a greater attraction held out for sheep and cattle to come to these once arid places. They assist the pro- cess by trampling down to a dead uniformity both the vegetation and the soil, while with their advent a new factor is introduced, namely the nitrates which result from the ammonia excreted by them, which foster the growth of the Poa and Dactylis, but are inimical to the older and rarer species. Nor must the influence of the atmosphere be forgotten. With the streaming rain and gentle dew a continual dissolving away and washing down of the original rock is taking place, and brought by the driving wind, particles of soil of a different character from the bed-rock are deposited. Before such agents as these the reprehensible maraudings of the too greedy botanical collector sink comparatively to nothing. Change of this kind is slowly taking place everywhere in Britain, but much more rapidly with us, since our rocks are all soluble, and the pro- cess is necessarily much more rapid than it is with the igneous rocks, which weather but slowly, and especially when the other factors of high cultivation, and a more densely populated area also are to be found. A similar process goes on in our small heathlands, and the introduc- tion or the increase of rabbits largely assists in it, since they nibble off very closely all the aboriginal vegetation, so that the annuals such as the bird's-foot trefoil {Ornithopus), the buck's-horn plantain {Plantago coro- nopus), the small trefoil {"Trifolium fiUforme) — the latter not yet recorded for Northants — have a very bad time, and only such hardy species as the ragwort {Senecio Jacobcea) appear to be able to hold their own ; while their rapid movements tend to distribute the nettles, the seeds of which get scattered from their furry coats. The stone quarries near Weedon, at Cosgrove, and heathy roadsides and heathlands of Holdenby, H addon, etc., are now much poorer than they were even in my recollection, and the mountain fern [Lastrea Oreopteris or Dryopteris montana) has been era- dicated. The broom {Sarothamnus scoparius) is now much scarcer, and its interesting parasite, the broom-rape {Orobanche Rapum-genistce) is now almost extinct. The replacement of stone buildings with those made of brick has caused a diminution in the number of mural plants. We read in Ray's Itineraries that he found on the walls of Northampton several interesting plants, and we know that the drawing of the wall pennywort or navel- wort {Cotyledon Umbilicus) in the first edition of English Botany was made by Sowerby from plants gathered on the walls of Peterborough Cathe- dral, but now few plants of any kind are found on the less congenial brick walls of Northampton, and the better state of repair in which the walls of Peterborough Cathedral are kept yield little space for the Coty- ledon, which it is to be feared has been quite exterminated there. Doubt- 53
