8 



YORKSHIRE NATURALISTS' UNION. 



2,000 feet. The best results were obtaitied, however, from 

 small, permanent, peaty pools containuig SpJtagnum fluiuosiim 

 and S. contortum, and from some of those rocks over which the 

 water incessantly trickles. It might not be amiss here to em- 

 phasize the Importance of these gatherings from vertical wet 

 rocks, as many of the rarest Desmids and the best Myxo- 

 phyceas are to be obtained from the gelatinous material of various 

 colours coating the surfaces of rocks constantly kept moist by a 

 thin film of water. The moorlands stretching in a westerly 

 direction from llklcy and Keighley are not so rich as the more 

 northern districts, and present a sameness and specific uniformity 

 wliich is markedly absent from the latter. 



The most productive grounds for l^esmids are those of the 

 Central Plain, the commons at Pilmoor, Strensall and Riccall 

 being parts of the primaeval boggy country, and both in then- 

 topography and alga-flora are very similar to the commons of 

 south-west Surrey. Unfortunately, Strensall Common has now 

 been drained for military purposes, and nearly all its fornier 

 treasures , have gone. Pilmoor, near Thirsk, is probably the 

 richest locality in Yorkshire for Desmids, above 130 species 

 having been found there, among which were many very rare 

 ones. Cocket Moss, near Giggleswick, is also a very rich 

 locality for this family of Conjugatas, and a boggy place about 

 two miles south of CIa])ham, on the way to Rowland Knotts, was 

 also productive of many uncommon Desmids. The best gather- 

 in<>-s from l)Oth Pilmoor and Cocket Moss were obtained from 

 Uiriadaria 7niiio?% The bogs and springs of Upper Teesdale 

 were found to be exceptionally \\v\\ in many of the uncommon 



species. 



The largest natural sheet of water in the county is Hornsea 



Mere, but it is comparatively poor in alg^, being similar in that 

 respect to the rest of the low-lying land in the East Riding. 



The list ofalgce published in Lees' 'Flora of West Yorkshire' 

 (1888) was very hurriedly put together; it was followed by 

 several other papers and notes referring to the alga: of Yorkshire, 



Trans. Y.N.U., 1896 (pub. Aug. 1900). Bot. Series, Vol. 5- 



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