INDUSTRIAL PROGRESS DURING THE YEAR 1875. ccxiii 



trees at Geneva. Both sets of branches were then placed in 

 a cold room until they were penetrated by the same temper- 

 ature, and then placed in glasses of water and removed to a 

 warm room. The result was that the branches from trees 

 growing at Geneva leafed out earlier by from eighteen to 

 twenty-three days than those brought from Montpellier. M. 

 De Candolle assigns two reasons for this precocity. First, 

 he thinks that there has been a natural selection of the buds. 

 The buds of a tree are in a continual struggle. The later, 

 like the badly placed ones, develop imperfect branches, which 

 are often stifled. The most precocious prevail, unless indeed 

 they suffer from frost. In this way comes a selection, and a 

 successive adaptation of the tree to the climate. How far 

 this selection applies is a little doubtful, for the precocity is 

 as likely to be disadvantageous as advantageous in a north- 

 ern climate. The cause of the difference in the vegetation 

 of northern and southern individuals is probably the more 

 complete hibernal repose of the former, rendering them more 

 susceptible to the heat of spring. 



Potato Rot, The oospores of the fungus which causes the 

 potato rot (Peronospora infestans) have been discovered by 

 Mr. Worthington Smith, of England. They are found in the 

 substance of the potato leaves, where they form black spots. 

 They occur more frequently in the leaves of American varie- 

 ties of potatoes than in others. The fungus was at first sup- 

 posed to be a Protomyces; but Mr. Smith, by macerating the 

 leaves, found bodies similar to those described by De Bary 

 as the oospores of species of Peronosporae. As a practical 

 result of this discovery, farmers need have no fear of plant- 

 ing potatoes after grain or clover, against which they had 

 been warned, as the rot is not propagated by these crops. 

 Also the stems and leaves of infected plants should be re- 

 moved as soon as possible. The potato rot made its appear- 

 ance in California, for the first time it is believed, in the 

 month of May last, at least two months earlier than its usual 

 appearance in the Middle and New England States. 



Plum-Pockets. The curious disease known in Germany as 

 Pflaumen Narren, or Taschen, was observed near Boston in 

 the month of June. The disease is caused by a fungus, 

 Ascomyces Pruni, which distorts the young plums, making 

 them appear at first swollen and then wrinkled. On cutting 



