142 JOURNAL OF THE [December, 



nothing in the case of the diatoms. They are simply plants, 

 notwithstanding the fact that one of our British cousins has re- 

 cently declared his belief in their animal nature. 



Eighth. The diatoms hold no insignificant place in the econ- 

 omy of nature. Their siliceous skeletons, deposited on the 

 bottoms of seas and estuaries in enormous quantities, have, in 

 places, built up geological strata of considerable importance. 

 These, having in some cases subsequently emerged, afford 

 material for several industries, among them the manufacture of 

 the polishing stone called Tripoli, and, singularly enough, the 

 manufacture of the terrible explosive dynamite. In their liv- 

 ing state, diatoms become food for a large number of animals : 

 for example, oysters and other delicious bivalves; also, acalephs, 

 which draw them into their stomachs in immense quantities and 

 thrive and fatten upon them, and which in turn, thus rendered 

 very acceptable, serve as food for the arctic whale. 



Note. — The foregoing paper was followed by the exhibition 

 of a large number of lantern slides, illustrative of the text, 

 photographed by Prof. W. Stratford. 



THE MAPLE LEAF-SCALE. 



BY PROF. SAMUEL LOCKWOOD, PH. D. 



{Read November ^th, 1886.) 



In the month of October last, Mr. F. W. Devoe sent me a 

 fragment of a maple leaf on which were several black, shiny 

 scales. I recognized the scales as those of the fungus, Rhytisnia 

 acerrimum, which, to some extent, had, for several seasons, at- 

 tacked the maple trees in the vicinity of my home at Freehold, 

 New Jersey. This is a fungus which has, unfortunately, become 

 too common. Its generic name is derived from a Greek word 

 signifying a patch or darn. During the past summer, the fine 

 maple trees for which Freehold is noted, were affected by this 

 fungus to an extent almost apalling. On some trees scarcely a 

 leaf was free from it, and upon each of some of the leaves were 

 as many as ten of these unsightly black patches. One windy 

 day the sidewalks presented a curious sight. They seemed to 

 be sprinkled with tiny flakes of anthracite coal, an appearance 

 caused by the falling of these patches of fungus from the dying 



