How to obtain it. 87 
growth of minute vegetable forms, varying in degree according to 
the nature of the water and the general surroundings, but the 
presence of some of the larger plants is greatly conducive to the 
health of the fish. Livingstone Stone says:—‘ Water plants 
consume carbon and return oxygen. Trout consume oxygen and 
return carbon. By putting plants and fish together, therefore, we 
avail ourselves of one of Nature’s great universal agencies, in 
balancing vital forces against each other, and maintaining the 
equilibrium on which the continuance of organic life depends.” 
Speaking broadly, this is so, and it must be remembered that 
some plants produce more oxygen than others, and some afford 
food and shelter to a much larger quantity of animal organisms, 
and every trout culturist nowadays knows the value of crustacea, 
mollusca, and of a great many of the lower forms of animal life, 
such as copepods, entomostraca, etc. 
The fly-fisher in comparatively barren lakes, knows how 
often in the neighbourhood of patches of aquatic vegetation, the 
best fishing is to be obtained. The cause of this should be 
noted. Shelter, food, and a greater abundance of oxygen are 
temptations which cannot be resisted by the fish, and conse- 
quently they are sure to be found in proximity to the vegetation 
which produces them. As on land so in water, some plants are 
more favourable to the production of food than others, and these 
are the plants to seek out and cultivate, due care being taken to 
study their life history, and to avoid as far as possible those which 
might, by spreading unduly, become a pest in the pond. There 
is one plant (Anacharis alsinastrum) to which I have already just 
alluded, which has been found such a pest in some places where 
it cannot be kept under. It should never, on any account, be 
introduced into waters where due control over it cannot be 
maintained. In places where it can be kept down easily it is, 
however, a most useful plant. I have seen some lakes very much 
spoiled by it, becoming quite choked, and an excessive amount of 
decay taking place continually, and rendering the water very 
unwholesome. In these places it sometimes unaccountably dies 
out. I have seen a pond quite cleared of it in this way for 
awhile ; but, a few small pieces retaining vitality will commence 
growing again, and spreading with rapidity, will soon choke the 
