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3. The inner and the outer walls of the peridial cells are 
much thinner than the corresponding peridial walls of the 
other rusts. The outer peridial wall of each clover rust is trans- 
versely striated while the inner wall is minutely papillose. 
4. The lumen in the cells of the peridium averages smaller. 
5. The openings of the aecia are smaller, the edges do not. 
recurve but incurve while those on T. repens recurve consid- 
erably, on T. pratense slightly or are straight. 
6. The paraphyses are longer, hymenial surface of the pycnia 
deeper than that of T. repens. 
7. The pycnia are taller and the osteoles wider than those 
of T. pratense, smaller than those of T. repens. 
8. There are as many morphological differences between the 
aecial and pycnial stages of the rust on T. hybridium and T. 
repens (also T. pratense) as between that on T . repens and T. 
pratense, which are regarded as two separate rusts. 
