NATURAL HISTORY OF THE DIATOMACEiE. 485 



When known, the name of the alga should be stated. If possible, it 

 is extremely desirable to secure specimens of diatom-encrusted algae in 

 spirits. In this way the diatoms will be preserved in almost their natu- 

 ral condition ; and those species, which are filamentous or grow in chains, 

 will be available in that condition for study. 



Fresh-water plants clouded with diatomacese may be collected and 

 preserved in the same manner as marine algae. As has been remarked, 

 the finer filamentous species of water plants yield the best results ; the 

 marine fucoids, as the "bladder wrack," and similar species, secrete a 

 mucus which seems to be repugnant to the growth of most diatoms ; yet 

 upon the stalks of Laminaria, and some other large olive-colored alg^, are 

 found the finer red-tinted species, which are themselves beautiful objects 

 of study, and are, in turn, the homes of hosts of minute forms of life. 

 Water plants, marine or fresh-water, should not be cleaned in any way, 

 but merely raised from the water, and, after draining for a short time, be 

 either laid upon a piece of clean paper to dry, or hung up where the air 

 and sun can rapidly evaporate the moisture. Marine plants will usually 

 not dry thoroughly, as the salts present in the water absorb moisture 

 from the air ; hence they are liable to mould unless they are packed in 

 paper. The moss-like carpeting seen upon submerged rocks is often 

 made up of beautiful specimens of the filamentous species of diatoms 

 alone, and it will be well to scrape the surface of the stone, and, placing 

 the mass in a bottle, cover it with alcohol, which will become colored 

 from dissolving the coloring matter of the diatoms, and preserve them 

 in the very best manner for future study. Fresh-water forms are very 

 often found hanging in green-colored festoons from the exit pipe of 

 drains, sluices, or fountains, and may be preserved in the same way. 



The green, brown, or fawn-colored scum which floats upon the surface 

 of the water of road-side pools, ponds, bogs, marshes, or rivers, consists 

 usually of little else but diatoms, and may be taken up by means of a 

 spoon or bottle, and then preserved in alcohol or dried upon paper. The 

 surface of the sea may be skimmed by means of a net of fine muslin, 

 having an opening left in the bottom, in which a four- or six-ounce wide- 

 mouth phial is tied, and towed at the stern of a vessel. If the sea-water 

 be strained through such a net, either by towing behind a boat or even 

 poured from a pail, the solid matter contained in it will be washed down 



