66 OF THE FILAMENTOUS ALG.E. 



inhabiting quickly-flowing streams. In most cases (es- 

 pecially with the species of Cladophora) the plant must 

 be gathered as near the point of attachment as possible — 

 the point, that is, corresponding to the root in a flowering 

 plant ; for, since the determination of the species depends 

 in great measure on the position of the main stem, its 

 degree of ramification, &c, it is by no means a matter of 

 indifference whether the whole plant or a mere fragment 

 be secured. This precaution is not so necessary with the 

 Ulothricaeese, as they consist of unbranched filaments. On 

 that very account they should be carefully collected with ' 

 the hand, not with the ladle, and then laid lengthways on 

 a strip of paper so as not to disturb the filaments, which 

 adhere but loosely together, and are easily separated and 

 carried away by the draining off of the water. 



If the tufts (as is often the case with the Vaucherise) are 

 dirty and discoloured, the mud and sand must of course 

 be washed off before the specimens are prepared for the 

 herbarium. They had better, however, be carried home 

 first, and thoroughly examined for Diatomacea?. It will 

 be time enough then to cleanse away impurities, taking 

 pains during the operation to avoid entangling the fila- 

 ments, and to preserve the natural habit of the plant. 



All the filamentous AlgaB may be laid out for ultimate 

 preservation on stout writing paper. The size of the 

 paper may be proportioned to the length of the object to 

 be laid on it. In practice, however, I have found the most 

 convenient form to be as follows : Let a half sheet of 

 writing paper be cut longitudinally into three strips, and 

 let each of these be again divided across the centre. A 

 sheet of paper will then give twelve portions, each of 

 which is of such a size as to lie comfortably on the palm of 

 the hand. The plants having been well cleaned from 

 fallen leaves, twigs, decayed matter, &c, and divided into 

 several distinct portions, are allowed to spread themselves 

 out on the surface of water in a large dish. One of the 

 portions is now taken out and made to float in another 



