X. INTRODUCTION. 



which corresponds with the more recent records of the 

 Meteorological Office. The mean temperature of the soil at 

 9 a.m., one foot below the surface, at Worthing, in 1884, was 

 52'6, and in 1885, 50'8. The Kew records, showing the 

 amount of bright sunshine in the South of England, and 

 which may be taken as approximately correct for Sussex, 

 give an average for 1880-5 of about 1,468 hours per annum, 

 an unusually large percentage, which, as influencing 

 vegetation, is of much interest. 



GEOLOGY, SOIL, AND SUBSOIL. The strata of Sussex may 

 be briefly stated as belonging chiefly to the Secondary 

 formations, comprising the Chalk, with flints and without, 

 the Chalk Marl, Upper Greensand, Gault, Shanklin or Lower 

 Greensand, Weald Clay, Hastings Sands and Clays, Tilgate 

 Forest strata and Ashburnham Beds ; the Tertiaries, in- 

 cluding Clay, Plastic Clay, and London Clay, which appear 

 only on the coast in the south-western extremity of the 

 county and in a few other isolated spots; and Alluvial 

 deposits, consisting of Diluvial and Alluvial debris, which 

 occur in the river valleys and bogs. In considering the soil 

 and subsoil with respect to the distribution of plant species, 

 we have those of the Downs, with a considerable tract of 

 moor, sandy-heath, and bog land at the foot of their 

 northern escarpment; the Weald, with its extensive woods 

 and forests ; the Forest Ridge ; a considerable amount of 

 Marsh land; and a long Maritime district of varied 

 character. Sussex, therefore, presents to the botanist a 

 diversified field for exploration. From Cooper's excellent 

 remarks on the Botany of the County, in the " Appendix to 

 Horsfield's Sussex, " the following summary is chiefly taken. 

 The Downs, which on the N. are steep and abrupt in the 

 direction of the Weald, descend on the S. with a gentle 

 declivity ; they vary from four to six miles in width. Their 

 summits are usually covered with a shallow layer of turf on a 

 thick covering of flints, the substratum being chalk. With 

 the exception of the hangers on their northern slope, they 

 are in general little wooded. On the hill sides the soil 

 becomes deeper and more suitable for tillage. To the W. of 

 the Arun the soil above the chalk is of a gravelly nature; 

 between the Ouse and the Adur the substratum is a reddish 

 sand. From Eastbourne to Shoreham the average depth of 

 the soil above the chalk is not more than four or five inches ; 

 from this westward through Arundel to Hampshire, it 



