ISA 



After the application of the spores the whole plant is covered with a 

 hell-jar and set in a shaded place for a period of three days. The bell- 

 jar prevents rapid evaporation, thereby securing the necessary condition 

 of moisture during the germination time of the spores. A certain amount 

 of warmth is desirable, but during the whole period the plants should be 

 screened from the direct rays of the sun. The bell-jars are temporarily 

 removed each day to allow a change of air and are sprayed on the inside 

 with an atomizer before being replaced. After the second day the plants 

 can be sprayed, but previous to this there is danger of washing away the 

 spores before there has been an opportunity for infection. On the third 

 day the bell-jar is removed and the plant changed to a location where 

 there is more light, in order that growth may be more normal and ob- 

 servation made easier. 



A label, bearing the date of the sowing and the name of the species 

 of rust, is a very valuable aid to the observer of results. If the infection 

 is a successful one the first signs are usually noticeable in five to ten days, 

 although some species require fifteen days or even longer. Ordinary 

 Puccinia and Uromyces species, such as the grass and sedge rusts, usually 

 develop pycnia in six or eight days, the aecia following about an equal 

 length of time. Some species, having only teliospores, show signs of in- 

 fection in four or five days by means of yellow spots, requiring twelve to 

 fourteen days to develop spores. Uredinia sometimes do not follow the 

 sowing of aeciospores for a period of fifteen days or more, while they will 

 reproduce themselves in five or six. The Gymnosporangiums show pycnia 

 in a few days and the mycelium may keep on producing pycnia for a con- 

 siderable period, but a month or two passes before the aecia appear. 

 Many of the species which produce their aecia on the evergreens germi- 

 nate their teliospores in the fall, but there will be no visible sign until the 

 aecia develop the next spring, as the pycnia are very inconspicuous. 



The procedure throughout is a simple one. No sterilization is neces- 

 sary, only care and cleanliness. The bell-jars are ready for use a second 

 time after a thorough washing. All organic matter should be removed so 

 as to avoid the starting of molds. No bits of rusted material can be left 

 on the pots or shelves near the plants without the liability of a stray in- 

 fection. As soon as a developing spore form becomes mature it should 

 be removed for the herbarium or separated from the plants not yet show- 

 ing infection. In all cases where it is the object to test the range of a 



