1884.] 



MICEOSCOPICAL JOUENAL. 



129 



Fresh Water Algae.* 



The term algas signifies sea-weeds, 

 and is used to designate certain ma- 

 rine and fresh-water plants, which, 

 because they bear no flowers, sta- 

 mens nor pistils, and in fructification 

 produce spores instead of seeds, are 

 styled cryptogamous plants. The 

 alg£e comprise not only sea-weeds 

 properly so called, but likewise the 

 gelatinous or scum-like substances 

 found floating on or near the surface 

 of ponds, ditch water, and placid 

 streams ; only a very small propor- 

 tion of the entire class of fresh-water 

 algae is confined to trunks of trees, 

 shady recesses, or to rocks dripping 

 with moisture. 



Owing to the life-like peculiarities 

 exhibited in some stages of their de- 

 velopment and growth many of the 

 algse were believed by Ehrenberg 

 and other microscopists of his time to 

 belong to the animal kingdom, but 

 the wholly vegetable character of the 

 algse is novs^ too well established to 

 admit of further controversy. 



Howsoever great in other respects 

 their individual differences may be, 

 the alg^ possess certain characteris- 

 tics which are common to them all. 

 They are cellular, flo'werless, and de- 

 void of roots ; their home is in the 

 water ; the veiy few which aflect 

 other localities die when deprived of 

 moisture. Their nutriment is ab- 

 sorbed through their entire surface 

 from the medium in which they live. 

 They are totally devoid of vascular tis- 

 sue ; in fact, are mere congeries of sim- 

 ple cells on the arrangement of which 

 depends their structural differences. 



As a large majority of them, espe- 

 cially the desmids, are free-floating 

 plants, it would be a waste of time to 

 seek them in rapid waters ; they aflect 

 pools, sluggish streams and ponds ; 

 the latter afford the most satisfactory 

 results to the explorer when the pond 

 is a mile or more in length and is fed 

 by one or two creeks ; the indenta- 



* Extract from 'Desmids of the United 

 States,' by F, Wolle. 



tions on the margins of such a pond 

 and its tributaries usually abound in 

 water grasses and mosses which shel- 

 ter and support the floating algse. 



The outfit need not consist of more 

 than a nest of four or five tin cans 

 (tomato or fruit) one within the other 

 for convenience of carriage ; ten or a 

 dozen wide-mouthed vials and a small 

 ring-net of fine muslin at the end of a 

 rod about four feet in length. Should 

 a boat be needed it can usually be 

 hired on the spot. After selecting 

 what seems to be a good locality, 

 drag the net a few feet among the 

 grasses and mosses above indicated, 

 allow the bulk of the water to drain 

 through the muslin, and then empty 

 the residue into one of the cans ; re- 

 peat this process as often as may be 

 desirable. Ten or fifteen minutes af- 

 ter the cans have been filled most of 

 the surface water may be poured oft" 

 and. the remainder transferred to a 

 glass vial, where the solid contents 

 will gradually sink, and the super- 

 ffuous water can be again poured oft' 

 and the vessel filled up with deposits 

 from other vials. In shallow^ places 

 what is known as swamp - moss 

 (ySphag?iui7i) ^ bladdei"wort {Utricti- 

 larta), Water-milfoil {JMyriophyl- 

 lum) or other finely-cut leaf water 

 plants are likely to abound ; these 

 should be lifted in the hand and the 

 water drained or squeezed from them 

 into a tin can, to be subsequently 

 treated as already stated. A few 

 drops of carbolic acid in each vial, 

 just enough to make its presence per- 

 ceptible, will preserve the contents 

 for months and even years from dete- 

 rioration ; the green coloring matter 

 (chlorophyll) may fade, but this in 

 the case of the desmids is of little im- 

 portance ; nevertheless, Avhen practi- 

 cable, aWays examine the material 

 when fresh. When dried on paper 

 for the herbarium, the specimens can 

 still, after being moistened with water, 

 be microscopically examined, but not 

 with the best results, since the drying 

 is apt to collapse or otherwise distort 

 the cells. 



