4 OF THE ALG.E GENERALLY, 



season after season, in the same situation ; while other 

 species, which were at one time just as abundant, have 

 entirely vanished, without any apparent reason. Take, for 

 example, Hydrodictyon utriculatum. It is quite astonish- 

 ing in what abundance this species will suddenly fill some 

 pond or ditch, at times almost obstructing the flow of 

 water, only to disappear again after a while without 

 leaving a trace behind. So that, if a person is anxious to 

 gather a large number of specimens (for the sake, say, of 

 making exchanges), he must be careful to do so while he 

 has the opportunity, and not leave them to a future period, 

 under the idea that they will await his convenience ; for . 

 he is likely enough in that case to deceive himself, and, on 

 returning to the piece of water, to find only emptiness, 

 where, the year before, there was superfluity. It is far 

 better to secure the requisite number of examples on first 

 coming across the species ; indeed, if necessary, the whole 

 stock may be taken, as there is little likelihood of extir- 

 pating any kind of Alga. 



What few implements are needed in the collection of 

 Algae are neither complicated nor expensive. The following 

 will be found useful : — 



1. A small iron or tin ladle, two inches across, fig. 7. 

 About one-third of the circum- 

 ference on the right hand side 

 is provided with a number of 

 teeth, three lines long, and bent 

 inwards. A short hollow handle 

 projects from one side of the 

 ladle, whereby it may be at- 

 tached to a walking-stick. 



This little instrument serves 

 to fish out plants which lie be- 

 yond arm's length ; and the 

 teeth may be usefully employed in entangling small species, 

 which occur on the surface of the water, such as Rivulariaa^ 

 Cylindrospermum, &c. 



