44 Plant-life of tJte Oxford District 



are left, as Reed-types (Equisetum}, free-floating (Azolla), saprophytic 

 (Psilotmri), xerophytic, epiphytic, and climbing (Lycopodium, Selaginella, 

 Lygoditim), while their prototypes of high forest have vanished, or only 

 remain in the form of coal. Similarly at the present day, convergence in 

 biological habit, or association in the same ecological station, is no indica- 

 tion of ' affinity ' or relationship. Existing families of Angiosperms may be 

 as remotely related as are the few residual types of Pteridophyta. Some 

 families are now left predominantly aquatic, others may be predominantly 

 or solely forest-trees ; others are now almost wholly herbaceous. The flora 

 of every country containing the essential biological stations is a complex of 

 the surviving protagonists, similarly specialized for their special problems, 

 along many lines of remote affinity. In all parts of the world the associa- 

 tion of similarly modified plant-forms in corresponding biological formations 

 gives a certain fades to the partial flora, which is distinctive ; though the 

 actual forms concerned may be phyletically wholly distinct, and making the 

 best in their own way of what equipment they may have inherited. 



The British Flora, as the deteriorated representative of deciduous 

 forest-land remote from the tropics, affords a wide range of biological 

 stations, woodland, open ground, and aquatic environment. It thus presents 

 a complex in which there is room for something of everything : all bio- 

 logical lines are represented, even if only by one or two forms in an 

 attenuated scheme. It still retains a few evergreen trees, now sub-dominant 

 to the main series of deciduous forest-forms. Underwood trees and shrubs 

 are well represented, with not only an abundant ground-flora, but a few 

 residual representatives of the secondary vegetation of the tropical forest as 

 parasites, epiphytes, saprophytes and liana-climbers. Open exposed ground 

 beyond the woodland area, gives an abundant variety of xerophytes in hot 

 summer : short-season plants mingle with the grasses of prairie-land ; all 

 grades of aquatic are met with in swamp-woodland, ditch, and open river. 

 The flora as a whole includes a series of samples, as the country itself affords 

 a wide series of samples of climate, geological formation, and botanical 

 stations. 1 



So far, again, no special reference has been made to the remaining 

 vegetation of older epochs in the evolution of the modern plant-kingdom, 

 as illustrated in the few residual Gymnosperms, the feeble representatives of 

 Pteridophyta, the wider range of Bryophyta (Mosses), and the numerous 

 and varied representatives of the still older range of Algae of freshwater 

 (including Plankton-forms), and their saprophytic homologues of the land 

 (as Fungi and Lichens). These are left for future consideration. The more 

 conspicuous and dominant forms of the modern flora have the first claim ; 

 this being the more emphasized by the fact that there is no evidence that 

 the full progression has taken place in this country, or through the inter- 

 mediary of any such archaic types. All are equally immigrant, and owe 

 their special characteristics to conditions of environment in probably far 

 distant lands. 



Owing to the local predominance of swamp conditions in the older 

 Oxford Valley, the progression of water-plants becomes of special interest, 

 as superimposed on the organization of the herbaceous forms of woodland 

 and woodland-swamp, introducing factors which are new rather than 

 regressive. But the general trend of events is so far outlined. Though 

 there may be indefinite breaks in the story of any given plant, as well 

 as divergence in special variations of the different problems, and it is 

 understood that the progression took place largely elsewhere before exten- 



1 Tansley (1911), Types of British Vegetation, p. 15. 



