1912.] PUBLIC DOCUMENT — No. 31. 109 



outdoor plants in the summer or early fall. It makes its ap- 

 pearance in the greenhouse in the late fall and persists during 

 the winter, affecting the leaves of the young, vertical shoots 

 more seriously than those of the older, pendant ones. We ob- 

 served both the euredospore and teleutospore outbreaks, which 

 occurred on the underside of the leaves on our material. In the 

 spring it appears to aifect the plants less seriously, probably 

 owing to the practice of frequently cutting off the affected parts 

 and destroying them, and to the vigorous growth of the plants 

 in the spring. When starting new plants care has been taken 

 to use only healthy cuttings from year to year, and in this way 

 the rust has, perhaps, been held in check to some extent. 



The disease affects both the green and variegated varieties, 

 although the latter are usually more severely affected. It has 

 been found on a large number of plants, but the loss has not 

 been serious owing to a tendency on the part of the plants to 

 outgrow the trouble. 



We have not been able to learn whether the mycelium is per- 

 ennial in the stem or not, or whether infection comes from the 

 field, but the rust does not seem to be so serious this year as the 

 past two years, agreeing in this respect with other rusts which 

 have been more or less epidemic. If the infection occurs on 

 outdoor plants, as in the case of chrysanthemum rust, it can 

 easily be controlled by indoor or tent-cloth culture, or by any 

 other means which would keep the dews off the plants, and even 

 if the mycelium is present in the stem to some extent the dis- 

 ease can no doubt be practically controlled by careful selection 

 of cuttings. We have been unable to trace the disease beyond 

 the points mentioned. The stock in use was obtained from the 

 immediate neighborhood where the infection occurred, although 

 no doubt the rust at some time or other came in on stock im- 

 ported from Europe. 



