6. The Lea.—The largest district, comprising the whole of the E. of the county. The London rocket (Sisymbrium irio) occurs only in the old towns of Hertford and Ware; the true oxlip (Primula elatior) near the head of the River Stort; a very rare broom-rape, Orobanche cærulea, at Hoddesdon, where it is parasitic on the milfoil; and an almost equally rare bedstraw, Galium anglicum, on an old wall of Brocket Park. A rare trefoil, Trifolium glomeratum, is known only at Easneye near Ware; and Hatfield Park is our only locality for the water-soldier (Stratiotes aloides) except where it has evidently been planted. Two species, usually of rare occurrence, Polygonum dumetorum and Apera spica-venta, are frequent in the district.
The indigenous flowering plants of Hertfordshire number 893 species, 679 being Dicotyledons and 214 Monocotyledons. If to these be added 199 aliens, etc., the total number of species recorded is brought up to 1,092. The flora is essentially of a southern type, the northern species being few in number. Owing to the dry soil, xerophiles largely prevail over hygrophiles.
The Ferns and their allies the horsetails and clubmosses are not well represented, both the soil and the air of the county being too dry for them. Another cause for the present scarcity of ferns is the proximity of Hertfordshire to London, for they have been uprooted and taken there for sale in cart-loads. We have twenty-four species of ferns and fern-allies, but not one really rare. The principal varieties are Scolopendrium vulgare, var. multifidum; Athyrium [filixfæmina], var. convexum; and Polypodium vulgare, var. serratum. Equisetum silvaticum is our rarest horsetail; and our only clubmoss is Lycopodium clavatum.
The Mosses are much better represented than the ferns, 175 species having been recorded. The bog-mosses are represented by six species—Sphagnum intermedium, cuspidatum, subsecundum, acutifolium, squarrosum, and cymbifolium. Tetraphis pellucida occurs in Sherrard’s Park Wood, and Polytrichum urnigerum in Hitch Wood. Seligeria pusilla has been found in an old chalk-pit in Brocket Park, and S. paucifolia on chalk nodules in the Tunnel Woods near Watford. Campylopus pyriforme occurs in Berry Grove Wood, Aldenham, and C. flexuosus in Dawley’s Wood, Tewin.
Of the Liverworts (Hepaticæ) forty-four species are known to occur; and the Stoneworts (Characeæ) are represented by seven species—two of Chara, two of Tolypella, and three of Nitella.
The Algæ have been pretty fully investigated, especially the Diatomaceæ, of the 252 species of Algæ known to occur in the county, 156 belonging to that interesting family of microscopic plants. As an illustration of their minute size it may be mentioned that a single drop of water from the saucer of a flower-pot at Hertford, mounted as a microscopic slide, was found to contain 200,000 separate frustules of Achnanthes subsessilis, and it was estimated that these occupied only one twenty-fifth part of the drop. Both species of Chlamidococcus (the old genus Protococcus), C. pluvialis and C. nivalis occur; and the pretty Volvox globator has frequently been found.
Of the Lichens much less is known, only sixty-seven species having been recorded. The most noteworthy are Calicium melanophæum, found on fir-trees in Bricket Wood; Peltigera polydactyla, on moss-covered ground in Oxhey Woods, Watford; Lecanora phlogina, in the Tunnel Woods, Watford; and Pertusaria globulifera, on trees in the same woods and also in Bricket Wood. As woods in the vicinity of Hertford and of Watford only have been searched for lichens, our list ought to be largely increased by investigation in other parts of the county.
Of the Fungi our chief knowledge is derived from lists of species collected at Fungus Forays of the Hertfordshire Natural History Society and from records of the Mycetozoa by Mr. James Saunders. The number of species recorded for the county is 735, of which fifty-eight are “myxies”. Of the Hymenomycetes, or mushroom-like fungi, some very noteworthy finds have been made, nearly all at Forays of the county society. They include two species new to Britain, viz., Agaricus (Nolania) nigripes, found in Aldenham Woods, Watford, and Ag. (Hypholoma) violacea-ater, in Gorhambury Park, St. Albans (by the present writer). Hertfordshire has also furnished the second British records for Ag. (Lepiota) gliodermus (Broxbourne Woods), Ag. (Leptonia) euochrous (Ashridge Woods), Ag. (Psathyrella) aratus (Sherrard’s Park, Welwyn), and Paxillus Alexandri (Hatfield Park), this species having first been recorded from Hatfield Park, Essex; and the second and third British record for Agaricus (Clytocybe) Sadleri (Ashridge Park and Cassiobury Park). The very rare Strombilomyces strombilaceus has been found in Grove Park, Watford, and the still rarer Peziza luteo-nitens on the Chalk slopes between Aldbury and Ashridge Park. Lastly it may be mentioned that Mr. Saunders added the “myxie” Physarum citrinum to the British fungus-flora from specimens found by him at Caddington and Welwyn.
The Birds of Hertfordshire have been carefully observed, and the appearance of rare visitors has been duly recorded. At a lecture delivered at St. Albans in 1902, Mr. Alan F. Crossman, F.L.S., F.Z.S., stated that 212 species had been known to visit the county, and mentioned, inter alia, that the kingfisher is more numerous in Hertfordshire than formerly, that the heron nested in the county for the first time in 1901, and that the appearance of the bearded titmouse had been noticed on but three occasions. During the last forty years the following birds, among others, have been noticed as occasional visitants: the storm-petrel (Procellaria pelagica), golden oriole (Oriolus galbula), whooper-swan (Cygnus musicus), snow-bunting (Plectrophanes nivalis), greater spotted woodpecker (Picus major), black tern (Hydrochelidon nigra), great northern diver (Colymbus glacialis), herring-gull (Larus argentatus), cormorant (Phalacrocorax carbo), tufted duck (Fuligula cristata), hoopoe (Upopa epops), crossbill (Loxia curvirostra), sheldrake (Tadorna cornuta), [guillemot] (Lornvia troile), Pallas’ sandgrouse (Syrrhaptes paradoxus), rock thrush (Monticola saxatilis), black redstart (Ruticilla titys), Dartford warbler (Silvia undata), grasshopper warbler (Locustella [nævia]), waxwing (Ampelis garrulus), twite (Linota flavirostris), hen harrier (Circus cyaneus), buzzard (Buteo vulgaris), redshank (Totanus calidris), greenshank (Totanus cunescens) and the little auk (Mergulus alle).
The lapwing is thought to be increasing in numbers; the writer frequently observed considerable flocks during his recent rambles in the county. Finches are perhaps as numerous in Hertfordshire as in any other county of equal size; the large flocks of hen chaffinches that haunt the farmyards in winter being quite a notable feature. The goldfinch, it is to be feared, is rapidly becoming scarcer; as are also the jay, the woodcock and other birds much more numerous a few years back. Fieldfares and redwings visit the county in great numbers from the N. during the winter; one morning in the winter of 1886 the writer saw many thousands of fieldfares pass over St. Albans from the direction of Luton. The redwing, being largely insectivorous, is often picked up dead in the fields when the frost is unusually severe and food proportionally difficult to obtain.