A HISTORY OF HERTFORDSHIRE 



The district drained by the Lea and its tributaries is about 500 feet in height on the 

 north, along the downs forming the water-parting between the catchment-basins of the 

 Thames and Ouse, the surface gradually sloping towards the south, until along the river 

 Lea below Hoddesdon the ground is much lower and flatter than in any other part of Hert- 

 fordshire. Most of the district is on the Chalk, much covered by boulder-clay, but south- 

 east of Furneaux Pelham, Much Hadham, Hertford, and Hatfield it is on the London Clay 

 and its narrow margin of Reading Beds. 



The old towns of Hertford and Ware are the only localities in the county for the rare 

 Sisymbrium irio, which sprang up in London after the great fire of 1666, whence its name of 

 London rocket. The true oxlip (Primula elatior) occurs only near the head of the Stort on 

 the borders of Essex ; the very rare Orobanche ceerulea only at Hoddesdon, where it is parasitic 

 on the milfoil (Achillea millefolium) ; and an old wall of Brocket Park is the only habitat of 

 the almost equally rare Galium anglicum. Trifolium gkmeratum is known only at Easneye near 

 Ware ; the only locality for Stratiotes a/aides, except where it has evidently been planted, is 

 Hatfield Park ; and the ponds on Hertford Heath lay exclusive claim to Carex bcenninghausiana. 

 Two species usually of rare occurrence (Polygonum dumetorum and Apera spica-venti) are frequent 

 in the district. 



The Lea district has the largest number of rare plants of any, and much the largest 

 number peculiar to it. The list is as follows 



RANUNCULACEJE 



Ranunculus diversifolius, H. Wats. 



lingua, L. 



hirsutus, Curtis (sardous, Crantz) 

 Helleborus foetidus, L. 



viridis, L. 



PAPAVERACE^ 

 Papaver Lecoqii, Lamotte 



FUMARIACE.S 



Fumaria Boraei, Jord. 



Vaillantii, Loisel. 



CRUCIFER^E 



Nasturtium silvestre, Br. 



amphibium, Br. 

 Sisymbrium irio, L. 



Sophia, L. 

 Erophila praecox, DC. 



Senebiera (Coronopus) didyma, Persoon 

 Lepidium ruderale, L. 

 Iberis amara, L. 



CARYOPHYLLEJE 

 Silene anglica, L. 



noctiflora, L. 

 Cerastium quaternellum, Fenlz. 

 Stellaria palustris, Ehrh. 



LEGUMINOSJE 



Trigonella ornlthopodioides, DC. 

 Trifolium subterraneum, L. 



ochroleucum, L. 



glomeratum, L. 

 Hippocrepis comosa, L. 

 Vicia (Ervum) gracilis, Loisel. 

 Lathyrus aphaca, L. 



(Orobus) tuberosus, L. 



silvestris, L. 



ROSACES 

 Rosa silvestris, Woods 



stylosa (v. systvla), Bait. 

 Cratsegus monogyna, Jacy. 



CRASSULACE/E 

 Sedum fabaria, Koch 



HALAGORE/E 

 Callitriche obtusangula, Le Gall. 



OHAGRAKIEB 



Epilobium roseum, Schreb. 



UMBELLIFER^ 



Bupleurum rotundifolium, L. 

 Carum segetum, Benth. 



(Bunium) bulbocastanum, Koch 

 Cicuta virosa, L. 



Sesseli libanotis, Koch 



RUBIACEA 



Galium Witheringii, Sm. 



anglicum, Huds. 



VALERIANE./E 

 Valerianella auricula, DC. 



COMPOSITE 



Pulicaria vulgaris, G<ertn. 

 Filago apiculata, G. R. Sm. 



spathulata, Presl 



gallica, L. 



Arctium intermedium, Lange 



nemorosum, Lej. 

 Centaurea calcitrapa, L. 

 Amoseris pusilla, Gaertn. 

 Crepis biennis, L. 



taraxacifolia, Ihuill. 

 Hypochaeris glabra, L. 

 Tragopogon pratensis, L. 



CAMPANULACE/E 

 Campanula rapunculus, L. 



PRIMULACE* 



Primula elatior, Jacq. 

 Anagallis caerulea, Schreb. 



