36 



THE AMERICAN MONTHLY 



[February, 



stances the same spiral movements, 

 and, unlike the tube produced by the 

 germinating Puccinia spore, it does 

 not, as a rule, produce secondary 

 spores. 



The association of Vadium with 

 Uredo (in some state or other, either 

 as Uredo, Puccinia, Uromyces, or Coleo- 

 sporium) upon the same plant, often 

 upon the same individual, and even 

 upon the same leaf, is a fact well- 

 known to practical mycologists. 



Of the thirty-two species of yEci- 

 dium enumerated in " Cooke's Hand- 

 book of British Fungi," this associa- 

 tion exists in twenty species. In some 

 cases we find in nature this exists very 

 closely, e. g., ^c. ranunculacearum, 

 D. C, and Uromyces ficarice, Lev., 

 ^c, epilobii, D. C, and Puc. epilobii, 

 D. C. ^c. compositarum, Mart., and 

 Puc. compositarum, Sch., are often 

 found upon the same leaf; while i°«r. 

 sparsa, Cooke, is expressly said by 

 Dr. Cooke to be "only found amongst 

 or near the oxolete pustules of ^ci- 

 diuTii tragopogonis, Pers. 



There is, however, a much wider 

 question broached when we come to 

 associate the yEcidium, known only to 

 exist upon an exogenous plant with a 

 Puccinia confined to endogenous 

 plants. In order to convince reason- 

 able minds, the evidence must be un- 

 impeachable and complete. No mere 

 coincidences, however numerous, can 

 per se be taken as conclusive." 



[A series of experiments is then de- 

 tailed in the original article, which 

 occupy too much space to be reprint- 

 ed here. As an indication of the 

 manner of experimenting, however, 

 the first one is given in full. — Ed.] 



Experiment I. — On i8th June, 

 1881, seven healthy young wheat 

 plants, about six inches in height, 

 were infected with the spores of ^ci- 

 dimn berberidis, which were mixed 

 with water, and freely applied to both 

 surfaces of the leaves, and particu- 

 larly to the angle which the blade 

 forms with the stem. The pots con- 

 taining the infected plants were cov- 

 ered by a large bell glass, and plung- 



ed, with great care, into the ground. 

 At the same time, eighteen precisely 

 similar wheat plants, grown from the 

 same seed, were placed in the ground 

 in a pot, and covered by a bell glass, 

 to be kept as check plants. The 

 JEcidium was obtained from North 

 Wooton, distanced three and a half 

 miles, and the spores were used for 

 inoculation within two hours from 

 the time they were gathered. A 

 number of them were at the same 

 time placed upon a drop of water 

 on a glass slide, and kept in a 

 damp atmosphere, for forty-eight 

 hours, when they were found to have 

 germinated freely, which was proof 

 positive of their vitality, and that 

 they had not been injured by removal. 

 Both groups of plants were watered 

 from time to time, which was done by 

 raising the edge of the bell glass cov- 

 ering them, an inch or two. At the 

 end of ten days the bell glasses were 

 removed, and the plants examined 

 daily. On the twenty-fifth day a sin- 

 gle spot of Uredo was observed upon 

 one of the infected plants; the others 

 all remaining free. On the thirtieth 

 day this leaf was removed and exam- 

 ined, and found to be veritable Uredo 

 linearis. On the thirty-second day 

 two more of the infected plants had 

 Uredo upon them, but it was now 

 found upon the check plants: that is, 

 in twenty-two days from the time 

 they were uncovered. On the forty- 

 third day the experiment was con- 

 cluded, when the whole seven of the 

 infected plants had Uredo upon them, 

 as well as sixteen out of the eighteen 

 check plants. 



The result of these thirteen expe- 

 riments may be thus summarized: 



Seventy-eight wheat plants were in- 

 fected with the spores of yEcidium 

 berberidis and ninety-eight similar 

 wheat plants kept as check plants 

 against them. Of the infected plants 

 seventy-six per cent, developed Uredo 

 in an average of 24.4 days. While in 

 the same period seventy per cent, of 

 the uninfected plants became spon- 

 taneously attacked by Uredo. One 



