IOWA ACADEMY OF SCIENCES. 173 



milk no dissolving of the casein. On sterile bread no effect pro- 

 duced, indicating no spore forms were present in the yeast. 

 Bread from a bakery where this yeast was used was the sample 

 tested that did undergo a slimy decomposition when placed 

 under warm conditions. 



These results show that bacteria capable of producing a 

 slimy decomposition are common in some of the brands of 

 yeast most widely used, and it is probably the source of con- 

 tamination in most cases. 



METHODS OF PREVENTION. 



The question of the prevention of this abnormal fermenta- 

 tion is one of considerable economic importance and probably 

 will continue to be unless the yeast companies put a purer 

 article on the market. The chief precautions that may be 

 taken to prevent the trouble, are to place the bread in a cool 

 place as soon as practical after baking. The bakings should 

 also be made small so that the bread will be consumed before 

 decomposition begins. If the trouble has occurred where 

 potatoes or potato water are used in any form, it would be 

 advisable to discontinue this use. So conducting the process 

 of making that the bread will not be very moist, will help to 

 prevent an occurrence of this trouble. No fear may be had 

 regarding the effect on the health from eating bread contain- 

 ing this putrefaction, as the bacteria proiucing it are harm- 

 less saprophytes and the products formed by the decompo- 

 sition are not known to be injurious. After the change has 

 reached the later stages, the taste, odor, and physical con- 

 dition are so marked that there is no difficulty in detecting it. 



ADDITIONS TO LICHEN DISTRIBUTION IN THE MIS- 

 SISSIPPI VALLEY. 



BRUCE FINK. 



During the last Cew years I have examined a large number 

 of lichens from various parts of the Mississippi valley, and 

 a few of these have never been recorded from the states in 

 which they were collected, either in my own papers, or, so 

 far as I know, in other publications. In a paper* read before 



• Fink, B. Notes on Lichen Distribution in tlie upper Mississippi valley. Memoirs 

 of the Torrey Bot. Olub. 6 : No. 5. 385-307. 1 D 1899. 



