10 INVESTIGATIONS OF RUSTS. 



Norton was examined and the pods were found to be badly affected. 

 Moreover, he stated that the seeds were planted without shelling. But 

 the writer did not know then, as he does now, that this fact would 

 probably make little difference, since the naked seeds are commonly 

 affected, often showing- actual peridia. 



To test the theoiy of rust propagation above mentioned, experiments 

 were instituted on April 22 for growing plants from rusted seed under 

 a bell jar. The seed used bore all stages of the rust. The experiments 

 were in five series: (1) Seeds shelled and disinfected by mercuric 

 chloric!; (2) seeds unshelled and disinfected; (3) seeds shelled, but not 

 disinfected; (1) seeds unshelled, not disinfected; (5) like series No. 1, 

 but rusted mainly with ascidium. All were planted in pots in a 

 greenhouse and the pots were kept under bell jars. On May 1 the 

 plants began to come up. After about three months, when the plants 

 had grown to a height of 3 to 5 inches, no rust had appeared on series 

 1 and 2, and only one spot on one plant of series 3. The plants of 

 series 1 and 5 were much rusted, the ascidium appearing first, fol- 

 lowed shortly by uredosori. 



On April 25, 1893, it was attempted to germinate teleutospores of 

 rust from the seeds used in these experiments, in water-drop cultures, 

 which resulted in failure. On June 28, 1893, a similar culture of the 

 fresh uredospores failed to germinate in two days. 



In 1895 rusted seeds of Euphorbia dentata, sent from Kansas, were 

 planted in the greenhouse of the Department of Agriculture, at Wash- 

 ington, D. C. From these three plants grew, which were kept under 

 a bell jar. Soon one of these plants rusted badly, first with the ascid- 

 ium, then a slight amount of the uredospores, and later the teleuto- 

 spores. It should be remarked here that Euphorbia rust, so far as 

 reported, occurs only on E. maoulata in the vicinity of Washington, 

 D. C, and the writer has never yet been able to obtain rusted seeds in 

 that region. - 



On December 11, 1896, a third series of experiments was started at 

 Washington, D. C. On that date rusted seeds of Euphorbia dentata 

 from Kingman and Manhattan, Kans., were planted and kept under a 

 bell jar as before. Eleven plants resulted by December 26. On March 

 8, 1897, spermogonia appeared in considerable amount on the } T oung 

 leaves of one plant, with a tendency to form a sort of hexenbesen. 



On March 29 two more plants were rusted, one with spermogonia 

 only on the } T oung leaves, and the other with aecidia on the fruit. 

 On April 10 still another plant showed spermogonia, making four in 

 all, out of the eleven, that became rusted. (See PI. II,. fig. 1.) 



As above stated, the proof that the rust actually penetrates the hulled 

 seed is readily obtained, not only from microscopical demonstration, 

 but also from the fact that the actual peridia ma} T often be seen with 

 the unaided eye in the seed. These experiments, however, further 



