THE PLANT WOKLD 89 



bed liad its cutting continued late for market, and a young vigorous 

 growth of brush stood about hip high. Looked at from one side, all the 

 main stems and branches were showing the rust just breaking through 

 the skin. On the opposite side the same stems had very little of the 

 rust in sight. The rusted side was toward the old bed, and it was fur- 

 ther observed that the sides of greatest rustiness made an arc the radii 

 of which centered in the old bed. The observation told much, for it 

 demonstrated that the infection was aerial and not through the roots. 

 It showed that the old bed was the source of the contagion, and that 

 the wind was the vehicle of transfer. The asparagus plants of the later 

 bed that stood in the line of the house were protected by it and showed 

 much less rust, and the same was true of the barn. There was a nar- 

 row belt between the two buildings where the disease was abundant, 

 and here the spores had uninterrupted access to the young asparagus 

 plants. 



This complete demonstration of the method of inoculation leaves it 

 easy to see how the disease maj be carried for long distances by the 

 same agency. It has been frequently observed that beds of asparagus 

 standing alone, and surrounded by forests, are much less likely to be 

 badly rusted than those in the full open. If the barberry-covered rocky 

 hillsides of New England can furnish the spores to inoculate with rust 

 all wheat fields within the sweep of New England winds, it goes with- 

 out further argument that the rust of the asparagus may have its spores 

 carried as far as the breezes go that blow across an infected area. 



Wlien an asparagus field is badly infested with the rust, the gen- 

 eral appearance is that of an unusually early maturing of the plants. 

 Instead of the healthy green color, there is a brown hue, as if insects 

 had sapped the plants, or frost destroyed their \dtality. Eusted plants, 

 when viewed closely, are found to have the skin of the stems lifted, as 

 if blistered, as shown in figure 1, a and b. 



The brown color is due to multitudes of spores borne upon the tips 

 of fine threads of the fungus, which center at certain points and cause 

 the spots. A view of a section through one of the spore-bearing spots 

 is shown at figure 2, /. The threads from which the spores are pro- 

 duced are exceedingly small, and grow through the substance of the 

 asparagus stem, taking up nourishment and causing an enfeebled con- 

 dition of the ^dctim, which results in loss of the green color and the 

 final mistiness of the plant, due to the multitudes of spores formed upon 

 the surface, shown by figures/, and g. These spores are carried by the 

 wind to other plants, where new diseased spots are produced; but as 

 the autumn advances, a final form of spore appears in the ruptures, 

 figure j, that is quite different in shape and color from the first ones 

 produced through the summer. At i, is shown a section of a rust rift, 



