5 6 Fibre Balls. [Sess. 



from 2 to 6 inches in diameter. They are principally com- 

 posed of the filaments of a fresh-water alga, Cladophora iEga- 

 gropila. The lake is about the mean level of the sea, and it 

 is stated that there are currents in it, flowing outwards and 

 inwards alternately, according to the state of the tide ; and 

 these balls appear to be formed by the consequent gentle roll- 

 ing at the bottom of the water. Probably, as the alga decays, 

 the filaments become slightly glutinous, and thus adhere 

 together. A good deal of mud and sand seems to be often 

 included in the balls, and sometimes two distinct balls form a 

 nucleus for a much larger one. The structure of the alga is seen 

 very distinctly under the microscope, when the balls have been 

 sufficiently softened by maceration. Usually each ball has a 

 series of felty coats about one-eighth of an inch thick. As the 

 balls dry, they shrink ; and when they are completely dry, 

 they are very much smaller than when they are first formed. 1 

 2. Balls of pine and larch needles. — These are found in 

 Loch Tay, usually from the 14th to the 16th of November, 

 after stormy weather. The President paid a visit to Loch Tay 

 in November 1892, for the purpose of obtaining specimens, 

 and found a large number in a small shallow bay about two 

 miles from Kenmore. The balls are very nearly of the same 

 specific gravity as the water, but a little lighter ; so that when 

 a large ball is thrown into the water, a very few fibres appear 

 above the surface. The balls while moist are very firm, and 

 are usually quite round, but are occasionally ovate. But when 

 the needles are dry, they shrink very much, and the balls must 

 be artificially confined to prevent their falling asunder. The 

 one in the Museum of the Edinburgh Botanic Garden is held 

 together by thin glue that has been poured over it; but a 

 better plan is to confine the ball in a fine net, such as is used 

 by ladies for their hair. These balls, like the Kildonan balls, 

 seem to be formed by a rolling motion. The waves raised by 

 the wind carry the pine needles forward on the top of the 

 water, and then drag them back along the bottom of the 

 shallow bay. The balls are found on the shore, embedded in 

 a bank of decaying leaves and other vegetable refuse thrown 

 up by the waves ; and they generally consist simply of the 



1 See also "The Green Balls of Locli Kildonan," in 'Trans. Field Nat. and 

 Micro. Soc.,' vol. ii. p. 420. 



