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Journal of Agricultural Research voi.xxvii.no.io 
had been formed, spreading away from the mouth of the cup (fig. i, 
A, B). These spores, mounted in water, appeared not to differ from 
ordinary aecidiospores, but examined dry directly on the slide on which 
they had been discharged, it was apparent that some of the spores had 
small spherical bodies attached to their walls. Many such granules lying 
scattered about over the field covered were at first thought to be particles 
of dust, but on going back to aecidia on fresh leaves and looking down 
into the aecidium cups it was found that the spores showed these bodies 
on their surfaces before being discharged. By carefully dislodging the 
bodies from the spores in dry mounts it became evident, as it had not 
been in liquid mounts, that some of them were located directly over the 
germ pores and that probably each germ pore originally was capped by 
one of these globules. The part that they might play in spore discharge 
became clear from a study of their development. 
Fig. i. —Gymnosporangium myricatum. A, B: Spore prints formed after dissecting out an aecidium, and 
laying it down on a glass slide in a damp chamber. The print was photographed and the diagram 
made from the photograph. Some of the spores were shot out distances equal to about ioo times the 
diameter of the spore. They might have been thrown farther if the aecidium had been placed some¬ 
what above the glass support. C: Outline of spores showing comparative sizes and numbers of plugs 
that still remained attached to the spores after their flight. 
Material for a cytological study of the bayberry rust was obtained by 
cutting out very small pieces of leaf or stem bearing young aecidia and 
fixing them in Flemming’s fluid. The triple stain differentiates very 
well the structures with which we are particularly concerned. 
Between the lowest spore cell being cut off from the basal cell and the 
outermost spore which is fully mature and is about to be discharged, 
there exists a number of spores in all stages of development (fig. 2). 
These spore chains are clearly prismatic in cross-section because they 
are under strong pressure, not only from the sides but from below as 
well, and the individual spores and intercalary cells are more or less 
angular in outline. Spores in adjacent chains are cut off at different 
