Hunting for Diatoms. 195 



Epithemia musculus, Amphora affinis, with Pinnularia Cyprinus 

 and peregrina. 



We now approach the banks of a canal, into which the 

 brackish water sometimes gains access. Let ns hook out some 

 of the Potamogeton and other weeds. "Well done, we have here 

 something that will reward us for our fatigue. Examine it 

 with the Ooddington ; the circular discs are valves of the rare 

 Cyclotella punctata. Mixed with these we find Campylodiscus 

 cribrosus, Bacillaria paradoxa, with a host of other both fresh 

 and salt-water forms. 



With the tweezers let us now carefully pull off some of the 

 brown tufts growing on the clay banks of the river. This looks 

 like some stunted Conferva. On examination with the lens, 

 the filaments are found crowded with rows of little sigmoid 

 things, for all the world like miniature specimens of Pleuro- 

 sigma Balticum. This is a prize again, being no other than 

 the rare Oolletonema eximium. 



Leaving this locality, let us proceed a few miles down the 

 river towards its embouchure, and where the water is Salter. 

 Being low tide, we see for miles the mud is coloured of a dark 

 chocolate-brown tint, owing to the presence of millions of 

 Navicula Jennerii. In the large lagoon, formed by the salt- 

 water getting over the embankment during spring tides, we 

 shall probably find an abundance of good things ; among these 

 many of the filamentous Schizonemas, Bhipidiphoras, and Po~ 

 dosphenias, and even Licmophora flabellata. Proceeding even 

 further down the river, the mud gradually disappears, sand 

 takes its place, and afterwards we come to the open sea, where 

 the coast is in places guarded by rocks. Here is a fine field for 

 the purely marine forms. Let us gather some of the wiry green 

 tufts of Cladophora rupestris, one of the best of the diatom- 

 bearing Algse. The tips of the Cladopliora are quite brown 

 with a parasitic growth of Grammatophora marina and maci- 

 lenta, together with Bhabdonema arcuatum, Gocconeis scutellum, 

 and Gomplwnema marina. On the other Algse, growing among 

 the rocks, we find masses of Podosphenia, and perhaps the easily- 

 overlooked Hyalosira delicatula. The brown hair-like mass 

 floating about, but attached to the stones, is Fragillaria stri- 

 atula, and some of the filamentous Schizonemas. 



In the rocky pools left by the tide are some masses of 

 Corallina officinalis, growing in dense tufts. This Algse is an 

 excellent diatom trap, collecting the floating frustules among 

 its tangled branches. We must, therefore, select a good stock 

 of the Coralline, lifting it out of the water with as little violence 

 as possible, for fear of washing off the diatoms. 



Washing afterwards in acidulated water will liberate the 

 frustules, and then we have probably a fine gathering of the 



