COLLECTING DIATOMS. 35 



Potamogeton and other weeds. Well done ! we have here something 

 that will reward us for our fatigue. Examine it with the Coddington ; 

 the circular discs are valves of the rare Cydotella 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 Pleurosigma Balticum. This is a prize 

 again, being no other than the rare Colletonema cximium. 



" 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 colored of a dark chocolate-brown tint, 

 owing to the presence of millions of Naviada Je?inerii. 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, Rhipidiphoras, and 

 Podosphenias, and even Lianophora 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 CladopJiora rupestris, one 

 of the best of the diatom-bearing Alga?. The tips of the CladopJiora 

 are quite brown with a parasitic growth of Grammatophora marina and 

 macilenta, together with Rhabdonema arcuatum, Cocconeis scutellum, and 

 Gomphonema marina. On the other Algae, growing among the rocks, 

 we find masses of Podosp/ienia, and perhaps the easily-overlooked Hyalo- 

 sira delicatula. The brown hairlike mass floating about, but attached to 

 the stones, is Fragilaria striatuJa, and some of the filamentous Schizo- 

 nemas. 



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

 officinalis, growing in dense tufts. This Alga 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 beautiful Eupodiscus 

 Ralfsii, with Eupodiscus subiilis ; perhaps also Amphiprora lepidoptera, 

 and other nood forms. 



