BOTANICAL GAZET7E. 142 



"The object of the present paper is to present in a popular form 

 a statement of what is known with regard to the effect of the growth 

 of different plants upon the water in the ponds, streams, and basins 

 which supply the cities and towns of the Commonwealth. In this 

 connection the subject will be discussed from a botanical point of 

 view; and we can only consider certain striking properties, such as 

 smell and taste, with relatiin to the particular species of plants which 

 produce them, without taking into account the more subtle changes 

 which can only be detected by chemical analysis. It is desirable that 

 all who, in any sense, have charge of the public health, should have 

 some familiarity with the common forms of plants, likely to pollute 

 drinking-water; because, as the matter now stands, the public are at 

 the mercy of any person, who, armed with a compound microscope 

 and a supply of Latin and Greek names, chooses to alarm the neigh- 

 borhood by the announcement of the appearance in the water-supplies 

 of plants whose injurious nature is supposed to be in direct propor- 

 tion to the length and incomprehensibility of their names. The public 

 are now beginning to read about the germ-theory of disease ; and 

 hearing that fevers may be produced by germs, and being told that 

 germs are found in water, they very naturally but illogically infer that 

 any small bodies found in the water are the germs of disease. What- 

 ever of truth there may be in the germ-theory of disease, there is no 

 doubt that designing persons impose on the credulity and fears of the 

 public by representing as germs of disease microscopic plants which 

 could not possibly have caused any of the diseases which have been 

 supposed by scientific men to be produced by germs of a vegetable 

 nature." 



After speaking of the higher water-plants, such as Myriophyllutn, 

 Anacharis and Fotamogeton, the writer p.oceeds to consider the algae. 



"Whatever their shape may be, we may, in considering the effect 

 which they produce, divide the algae into two groups : those which 

 are grass-green or yellowish-green, and those which are bluish-green 

 or purplish." 



"Considered from a sanitary point of view, we may say that the 

 grass-green alg^e have no injurious effect upon the water in which they 

 grow On the contrary, we may regard their presence as an indica- 

 tion of its purity, for they do not grow in impure water. If almost 

 any river or pond water, no matter how clear it appears, is placed in 

 a covered glass jar, in a few days or weeks there will be formed a 

 greenish expansion on the sides and at the bottom, which, on exami- 

 nation will be found to consist principally of the young stages of de- 

 velopment of some of the alg^e which we have already described." 



"We may next pass to a consideration of those algae which have 

 a bluish-green color. The color is of importance, because by its 

 means, any person of ordinary intelligence can distinguish the present 

 group of algas from tho-e already described; and while, as we saw, 

 the latter are quite harmless, it is to the presence and decay of the 

 former that we are able to ascribe the cause of some of the most 

 •decidedly disagreeable odors and tastes found in drinking water." 



