356 THE SEA SHOES 



be found in most rock pools, from near high -water mark down wards, 

 the smaller and more delicate forms adding much to the beauty of 

 these miniature seas ; but the largest and many of the prettiest 

 species exist only at or beyond the lowest ebb of the tide, and hence 

 the algologist, in quest of these beautiful plants, will find it necessary 

 to work at the very lowest spring tides, with the occasional aid of a 

 small boat drifted into the narrow channels among outlying rocks, 

 and a long hook with which to haul up submerged specimens ; and 

 it will also be advisable to search the line of debris at high-water 

 mark after stormy weather for rare weeds that may have been 

 detached and washed ashore by the angry waves. 



"While engaged in the former of these employments the search- 

 ing of outlying rocks with the boat and also when examining the 

 outer rock pools which are disturbed by the waves that wash over 

 their banks, the simple instrument known as the water-telescope 

 will prove invaluable. Everyone must have noticed how difficult 

 it is to observe objects in water, the surface of which is disturbed 

 by the wind or some other cause ; but the simple appliance named, 

 consisting only of a long tube of metal, a few inches in diameter, 

 and painted a dead black inside, will enable the observer to see all 

 submerged objects with the greatest of ease when the water is itself 

 clear. The principle of the water-telescope is as simple as its con- 

 struction ; for the tube, protecting the surface of the water within it 

 from the disturbances outside, prevents the light from being refracted 

 successively in different directions, while the dead-black surface of 

 the interior prevents those internal reflections that would otherwise 

 cause the vision to be indistinct. 



A few hours spent with the rhodosperms at the sea-side will 

 be sufficient to show not only the great variety of their form 

 and colouring, but also that the same species may vary according to 

 the position in which it grows. Most of the smaller forms are 

 delicate and filamentous, but others have expanded fronds which are 

 very leaf-like. The brightest colours are usually to be found at or 

 beyond low-water mark, where the weeds are covered with a 

 considerable height of water for hours together, and also in shady 

 situations at higher levels, while some of the species that grow in the 

 upper rock pools are often of such a deep colour, with so much 

 admixture of brown, that they may be easily mistaken for the olive 

 melanospores to be presently described. 



Most of the rhodosperms are attached directly to the rocks, and 

 the larger species have often a root-like disc by which they are very 



