34 COLLECTING DIATOMS. 



ellipsis. On another wooden breakwater we find Pleurosigma scalprum 

 and Navicula mutica. 



" Leaving the immediate vicinity of the docks, we come to a maze 

 of ditches, to which the salt water has access during spring tides, and 

 these ditches are often very rich in Diatomaceag. Let us commence 

 operations here by collecting this brown covering from the mud. Here 

 we have Pleurosigma angulation, fasciola, Slrigilis, Hippocampus, Nitzschia 

 sigma, and Surirella gemma. Such gatherings may afterwards be entirely 

 cleaned from the mud by covering the outside of the bottle with black 

 cloth, and letting it stand for some days in the sun. The diatoms 

 by this time will have worked themselves to the surface, and the thick 

 brown layer will be found quite free from impurities. This plan, if 

 carefully carried out, rarely fails. The brown floating scum must by 

 no means be neglected, for on bottling some we find we have secured 

 a good gathering of Pleurosigma fasciola, macrum, and delicatulum, with, 

 perhaps, Navicula ambigua, and other good things. 



" Proceeding to another ditch, we will take a dip from the mass 

 of brownish stuff which coats the weeds. Well, here indeed is a capital 

 haul, for we have Nitschia bilobata, Brebissonii, vivax, with Tryblionella 

 gracilis, Navicula a/nphisbcena, Pinnularia peregrina, and Cyprinus. 



" Further on we pull out some of the weeds which are covered 

 with brown furriness, and we have a gathering of Synedra fulgens and 

 Amphipleura Danica ; while on the mud we obtain a copious one of 

 Stauroneis salvia, Nitzschia dubia /3, with Navicula minulula. 



"But what can this brown hairlike mass be, growing parasitically 

 on the reeds and floating pieces of stick? On examination it will 

 prove to be pure Melosira Borrerii, which we will bottle up with 

 great satisfaction. 



" Further on we come to a large lagoon, and find therein some 

 plants very promising in appearance, and well worth gathering. These 

 yield us afterwards a fine mass of Amphiprora alata and paludosa, 

 Pleurosigma strigilis, Amphora salina with Surirella Brighttvellii. 



" Mind how you step over this boggy ground, with the ink-black 

 mud, smelling so unpleasantly of sulphuretted hydrogen. In spite of 

 the smell, we shall probably get something to reward us. Collect 

 carefully the brown covering from the mud, and you may find Navicula 

 elegans, lumens, Nitzschia dubia, 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 us hook out some of the 



