A HISTORY OF HERTFORDSHIRE 



PHANEROGAMIA 



The most interesting questions to determine with regard to the 

 flowering plants of our county are how and when they were introduced, 

 and what changes have taken place, or are doing so, in the character of 

 the flora. It is essentially of a southern type, possessing but few northern 

 species, and these are ' mostly rarities and numerically quite insufficient 

 to modify the aspect of vegetation.' 1 To show what is meant by this 

 it is necessary to state that the flora of Britain is a derived one, having 

 originally been introduced from the continent of Europe somewhere 

 about the Glacial period, with many subsequent accessions. Most of 

 our commoner species have come from central Europe, whence they have 

 spread over the whole of the British Isles, some northern species having a 

 Scandinavian origin and some southern species having migrated from 

 France and Spain. It is these which greatly predominate over the 

 northern species in Hertfordshire. 



The introduction of some of our existing species may date from 

 before the Glacial period, part of our small arctic flora may have been 

 introduced from the Scandinavian peninsula during this period, but by 

 far the greater number of our widely diffused plants appear to have 

 followed the retreat of the ice towards the close of the Glacial period, 

 migrating into this country from the great Germanic plain. Although 

 at that time the present main features of the surface of the county had 

 been impressed upon it, sub-aerial denudation has been actively going on 

 for the countless ages during which man has been upon the scene, and a 

 vast amount of material has been removed. But this erosion has been 

 effected by our existing rivers flowing in the same general direction as 

 they do now, though at higher and higher levels as we trace them back 

 in time. The flora of the county would not necessarily be thereby 

 affected, but it has doubtless been modified to some extent by the clearing 

 of forests and the draining of land. 



Hertfordshire was undoubtedly much more densely wooded in past 

 times, even within the historic period, than it is now ; the sources of our 

 rivers were much higher ; streams ran down many valleys which are now 

 dry ; and early man had to seek the higher ground away from the 

 morasses which have left evidence of their former existence in beds of 

 peat, or perhaps as elsewhere to seek safety from the wild beasts which 

 prowled over the country by erecting his dwellings over lakes which 

 have long ceased to exist. 



That the flora of Hertfordshire between the close of the Glacial 

 period and the advent of man was not widely different from what it is 

 at the present day may be gathered from the following list of flowering 

 plants determined by Mr. Clement Reid from the ancient lake-bed at 

 Hitchin : 2 Ranunculus aquatilis (aggregate), R. sceleratus, R. repens, Montia 



1 Flora of Hertfordshire, p. 558. 



'The Palaeolithic Deposits at Hitchin,' Trans. Herts Nat. Hist. Sac. vol. x. pp. 18, 19 (1898). 



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