90 THE PLANT WORLD 



witli the spores of late autumn, wliicli, from their dark color, give an 

 almost black appearance to the spots as seen in h. 



There is another form which the rust fungus assumes, not usually 

 seen in the asparagus field, but it may be found in early spring upon 

 plants that are not subjected to cutting. This is the cluster-cup stage, 

 so named because the fungus produces minute cups from the asparagus 

 stem and in small groups of a dozen to fifty, making usually an oval 

 spot easily seen with the naked eye. At c, figure 1, is shown a portion 

 of one of these cups, with the spores that are formed in them enlarged, 

 at d. This stage of the fungus comes first in the order of time in the 

 series, and is met with upon volunteer plants that may grow along the 

 roadside or fence row or in a field where all the old asparagus plants 

 have not been destroyed. This form of the rust was quite common 

 upon plants in vineyards and orchards set upon old asparagus fields 

 and the plants near the trees or trellises, out of reach of the cultivator, 

 were left to grow. The importance of a knowledge of the relation of 

 these cluster cups to the asparagus nist proper, will be dwelt upon 

 under the head of remedies. 



It is a pleasure to record that a parasite has been frequently seen 

 upon the uredo form of the asparagus rust. This is a fungus bearing 

 the name of Darluca filivm Cast., that is well understood as preying 

 upon the rusts generally. To the naked eye, the fungus, as seen in the 

 field, gives the rusted plant a mouldy appearance. This light-gray 

 color is due to multitudes of fine, curved threads that ooze out of the 

 more deeplj^-seated portion of the fungus. When these minute spirals, 

 made up of spores that, with the accompanying jelly, are pushed out 

 of the spore cavities, are washed away by rains, the asparagus stems 

 aj)pear covered with minute dark pimples, which are the spore cavities 

 of the fungus. The intimate association of the Darluca with the rust 

 fungus is shown at figure 3, where, at a, is given an enlarged view of a 

 spore rift of the Puccinia, within which there is a large number of the 

 dark spore cavities of the Darluca. The fine threads of the latter fun- 

 gus fasten themselves upon those of the rust and there finally results 

 the structures for spore production as shown at h, in a sectional view of 

 a rift. 



The two fungi, namely, the rust that feeds upon the sap of the 

 asparagus, and the Darluca that gets its nourishment from the filament 

 of the rust, are quite unlike in many things. The spores of the Dar- 

 luca, shown much enlarged at c, are colorless and boat-shaped, with a 

 cross- wall dividing each into two nearly equal parts, and therefore very 

 different from the large, oval, thick-walled, orange-brown spores of the 

 rust. Again, the method of their production is within a pear-shaped 

 cavity, while the rust spores are formed upon the free tips of the 



