20 PHYSIOGRAPHY OF THE EAST RIDING. 



such lacustrine remains, which appear lying in depressions 

 or alluYial hollows of the boulder clay. The beds are of 

 varying; thickness, and in descending order consist of — 



1. Surface soil. 



2. Peat, with remains of trees. 



3. Shell marl (fresh water). 



4. Boulder clay. 



As bearing upon the origin and history of certain mem- 

 bers of the flora, it may be stated that these lake deposits 

 are the only strata in the East Riding of interest to the 

 palaeo-botanical student, containing as they do the nearest 

 approach to fossil vegetation. In Mr. Clement Reid's 

 "Geological Memoir of Holderness " (1880), and also in his 

 more recently published "Origin of the British Flora" (1899), 

 lists of plant remains from these old lake-beds are given, and 

 include such species as the Arctic birch [Betida nana), bird 

 cherry (Pnuius padiis), oak, hazel, &c. The first of these is, 

 of course, extinct as a living plant in Holderness, and the 

 bird cherry, if indeed indigenous, is now very rare. To these 

 ma)- be added another tree, very common in the peat of the 

 cliff sections, as well as in such localities as may be dug into 

 for brick-making purposes. The tree referred to, the Scotch 

 fir {Pimis sylves/i'is), still grows in many places both east 

 and west of the Wolds, and from its remains in the peat it is 

 more than probably quite indigenous. 



Of the lakes themselves that were once so conspicuous a 

 feature in ancient and pre-historic Yorkshire, only one now 

 remains in Hornsea Mere, still the largest sheet of fresh 

 water in Yorkshire, being one and a half miles long by 

 half a mile broad. All the others, together with their accom- 

 panying marshes, have been largely drained by the intricate 

 network of dykes and open drains that intersect the basin 

 of the River Hull; and Holderness is no longer "the 

 merschlie londe " of Chaucer's time. Still there are many 

 patches of marsh and bog, and land in the next stage to 

 these, namely, the frequent low-lying and damp "carrs" and 

 "ings." Instances of these occur by the River Hull and its 

 tributary streams, canals, and drains near Driflield, Wans- 

 ford, Arram, and Leven, and,, less closely related to the 

 river, at such places as Marton, Keyingham, and Cottingham. 

 Watery places, more or less artificial, however, are plentiful 

 enough in this division owing to the above-mentioned system 

 of drainage, and in their waters and precincts still linger 

 many of the hydrophytes (aquatic plants), lineal descendants 



