28 VEGETATION OF BLAKENEY POINT. 



purposes of reproduction, and even so occasionally suffer 

 considerably in consequence. 10 



It is worthy of note that only those species attain any degree 

 of frequency which in one way or another are adapted to the 

 strenuous conditions which characterise this class of habitat. 



It is not in the scope of the present paper to treat in detail 

 of the cryptogamic flora, but before leaving the main bank it 

 may be said that where extreme stability obtains, as in the 

 shelter of the dunes or on the barer shingle of the lateral hooks, 

 lichens are of frequent occurrence. Of these the more im- 

 portant pioneer species are Buellia colludens and Rhizocarpon 

 confervoides which are most frequently followed by Lecanora 

 atra and Physcia parietina. 



II. THE LATERAL HOOKS. 



As the flora of the lateral banks will be treated with 

 greater detail in another connection, we shall only give here a 

 general account summarising the observations on all the banks. 



Whilst the main bank is essentially a shifting formation, 

 the laterals, though belonging to the same class, are relatively 

 stable, and associated with this greater fixity we find not only 

 that colonisation has proceeded much further, but also the 

 somewhat indefinite character of the distribution on the main 

 bank gives place to a much more clearly marked arrangement. 

 No fact could emphasise this more than the repetition on each 

 of the successive banks of the same sequence of zonations ; so 

 that, in general, an examination of any single hook gives 

 broadly the essential features of all. 



Viewed from the aspect of their conformation we can dis- 

 tinguish three main parts consisting, respectively, of the sloping 

 sides (these are steeper on the face directed towards the free 

 end of the main bank and usually very gentle on the opposite 

 face) ; the crest, forming a flattened or slightly convex top to 



10. The following is an extract from Professor F. VV. Oliver's field note book for 

 July 13, 1909. " Rumex after storm (N.W.) of July 7, most spikes of Rumex 

 hanging brown or dead (wind, or wind with salt ?). Tho.'e under the protection of 

 Suseda fruticosa, etc., uninjured. The Rumax was all right on the 6th, so this fixes 

 cause of damage." 



