THE PLANT WOELD 91 



tlireads. Both are fungi; botli are found in the same diseased spots of 

 the asparagus; but under the microscope the differences are as great as 

 between asparagus and onions, for both of the latter belong to the same 

 famil}^ of flowering plants (Liliaceae), while the Darluca and the rust 

 are members of widely-separated families of fungi. 



In some localities this parasite upon the asparagus rust has been 

 so abundant as to make it difficult to find a fully-developed rust spot 

 free from the Bruiuca. Microscopic study of this fungus has not ex- 

 tended far enougli to warrant any opinion as to the amount of influence 

 it has in checking the growth and spread of the rust, and as 1897 was 

 the first season that the Darluca has been met with, it is impossible to 

 make any statement as to the favorable effect its presence may have 

 upon the following crop. But upon general principles, the Darluca 

 may be looked upon as a friend by the asparagus-growers, and its pres- 

 ence in the rusted field is to be encouraged. 



This view of the Darluca opens up a further consideration of the 

 subject of spraying, for it is to be expected that the spores of the Dar- 

 lura, from their smaller size and thinner coat, would be more quickly 

 killed by the fungicide than the larger, thicker-walled spores of the 

 rust. It is possible, therefore, that it might be a disadvantage to spray 

 asparagus plants that are already covered like a mould with the spores 

 of the Darluca. In short, the grower is in a dilemma, and it is not 

 safe with the present limited knowledge at hand to decide satisfactorily 

 for him. It is true that the rust comes before the Darluca, and if the 

 rust fails to appear, there is no use for the Darluca. If early spraying 

 has only a small retarding effect upon the rust, but kills off effectively 

 the Darluca that might otherwise make a vigorous attack upon the rust, 

 it is possible that spraying to check the rust might defeat its own end. 

 It is clear, therefore, that the whole question must be left open until 

 further experience is had, and experiments made with the case. 



Another natural enemy of the asparagus was found in the early 

 part of the season upon the cluster-cup form of the asparagus rust. 

 This is the fungus Tuhercularia persicina Ditt. Figure 4, d, shows a 

 l)iece of asparagus stem with a cluster of the cups in the center, and 

 around this are five spore-bearing patches of the parasite, which are 

 large, irregular and black where the skin of the asparagus stem has 

 been broken. 



A x:)ortion of one of the spore-jjatches is shown in sectional view at 

 e, where the spores in great numbers are to be seen produced upon the 

 ends of threads. The spores are oval and purplish, and are shown 

 highly magnified at/. 



If the cluster-cu]) stage is essential to the development of the aspar- 

 agus rust and must precede it, this Tuhercularia, preying upon the 



