76 THE AMERICAN MONTHLY [Mch 



firm small circular colonies on peptone gelatine and vice- 

 versa. These differences appear to be due to the presence 

 or absence of a gelatinous sheath investing the rods, and 

 always accompanying a vigorous growth in the presence of 

 carbohydrates, especially cane sugar. The gelatinous 

 sheath is very evident when grown on potatoes, and the 

 growth becomes quite viscous. When grown in peptone 

 gelatine and other media devoid of carbohydrates, the 

 sheath is much reduced and the growth is neither gela- 

 tinous nor viscous. The gelatinous sheath is very evanes- 

 cent. It gradually disappears with repeated cultures even 

 on saccharose gelatine, in two or three transfers assumes 

 the form and size seen on peptone-gelatine. Special media 

 and age greatly influence motion of rods. In saccharose 

 broth they are actively motile. Involution forms are 

 produced in great numbers under unfavorable conditions 

 and in old cultures. In one end of the rod an oval high- 

 ly refringent spore is produced. The species is clearly 

 allied to B. subtilis,B. megatherium, and B. meseutericus. 

 Influence of Pure Metal on Plants. — Copelandand 

 Kahlenberg give an abridged account in the Pharma- 

 ceutical Review (17: 548) on the above topic. Frequent 

 observations have been made showing the tendency of 

 distilled water to be injurious to certain plants. Every 

 metal in contact with water and air is subject to some 

 change. When this chemical action is sufficient for the 

 effect to become visible the metal is tarnished or corroded. 

 The salts formed under such conditions are known to be 

 poisonous. Some metals are more resistant to corrosion 

 than others, e. g. gold, platinum and silver. The authors 

 conclude that those metals poison plants when present in 

 water whose salts are known to be toxic, the salts act- 

 ing in their ordinary characteristic ways, kill the plants. 

 In plant toxicology as well an animal toxicology, the 

 phenomena of stimulation and of poisoning are intimate- 

 ly related. The proper application of copper stimulates 



