W. WEST AND G. S. WEST : ALGA-FLORA OF YORKSHIRE. 7 



as little mud as possible, and allow the water to drain away for 

 about a minute or more; they should then be gently squeezed 

 over a wide-mouthed bottle, allowing the issuing water to collect 

 in the bottle. For several reasons the bottles should not be 

 filled quite full. We have known about a thimbleful of such a 

 slimy squeezing to yield more than a hundred (or even three 

 hundred) species and many thousands of individuals. This is 

 exceptional, however, and as a contrast a similar squeezing from 

 another locality might yield hardly more than one or two species, 

 and these of the commonest. 



If possible, algse should always be examined when freshly 

 gathered, as many of them are more easily determined in the 

 living state. It may be as well to note, however, that a large 

 number of the DesmidicEe, especially those with characteristic 

 surface markings, can only be determined with precision from 

 dead, empty cells, or semi-cells. 



Algae of all kinds are best preserved by adding to the water 

 in which they are living an equal volume of a weak solution 

 (about 2%) of potassium acetate (to which has been added a 

 minute quantity of cupric acetate). They may also be preserved 

 by adding a few crystals of carbolic acid to the fluid containing 

 them (about six or eight grains of crystallized carbolic acid to 

 each ounce of liquid), but the outlines of the cells have not the 

 clearness shown by those preserved in potassium acetate. Most 

 algae are much better for examination when preserved in a fluid 

 medium than when dried. On drying they usually collapse, and 

 on being soaked out they very often do not reattain their original 

 torm. Most of the Myxophycese, however, can be preserved very 

 well by drying, and at the same time they retain their bright 

 colours, this being a distinct advantage over those preserved in 

 fluid. 



Most of the mountain tarns are but poor collecting places, 

 the best being Oughtershaw Tarn (Mid-West Yorks.) and 

 Hunter's Hole, Craydale Moor (North- West Yorks.), both of 

 which are in the midst of deep peat at an elevation of about 



