216 
Journal of Agricultural Research 
Vol. XXV, No. 5 
no hyphae, but several hyphae having haustoria could be seen running 
between the cambium and phloem of the cane near the point of origin 
of this bud. It is clear that if the bud had developed it would not have 
been infected because of the very effective barrier of indurated tissue 
which was present between the hyphae and the bud. The next year 
an uninfected cane would have been seen in a hill where the other canes 
were rusted. The location of the mycelium in the stolon was also 
determined by sections at O, K, and K'. In each place the hyphae 
were confined to the region of the cambium and phloem, being absent 
in the pith wood and cortex. Sections of the basal portions of the in¬ 
fected shoots F, I, and C showed that the mycelium is much more gener¬ 
ally distributed in the pith, phloem, and cortex of these young structures. 
The absence of mycelium from all tissues at A and B and in the dormant 
bud L, taken in connection with the general distribution of hyphae in 
the shoots, indicates that this plant was first infected in an axial bud 
which later gave rise to a shoot such as F. The mycelium after entering 
the tissue at the base of the bud made its way along the cambium and 
phloem in both directions, entering new bud primordia as they developed 
in the region where the tip was taking root. The growing tip of the 
stolon was not infected, for no hyphae were found in cross sections 
at A. It is clear for the following reasons that the experimental plants 
were rust-free when inoculated: (i) The parent plants have been 
observed in the greenhouse three years, and still show no rust. (2) No 
mycelium was present in sections of the stolons giving rise to the experi¬ 
mental plants, these sections being made from pieces killed at the time 
the new plants were cut away from the parent. (3) A second series 
of sections was made from the piece of stolon attached to the new plant 
after the rusted leaves had appeared the following spring. These parts 
contain no mycelium. (4) Sections of the tip ends of such stolons as 
continued growth after rooting showed no mycelium. 
Further investigation proves that it is essential to section the stolon 
only at the place where it has taken root or where the infected shoots 
originate, in order to determine whether a rusted tip-plant has been 
primarily infected by sporidia, or has been invaded by hyphae from 
its infected parent. If there are no hyphae in the central pith of the 
parent cane where it roots one can rest assured that it is a case of in¬ 
fection by sporidia. The mycelium will then be found along the cambium 
and phloem. 
During the time in which the tip of the stolon is establishing a root sys¬ 
tem, buds are also developing. Since the fundamental parenchyma of the 
bud primordium at this time is not well protected with scales and the 
wood ring is still unformed, hyphae from spores falling on these parts 
might easily find their way into the growing regions and penetrate to 
practically all parts of Jdiese buds, and from here grow back along the 
cambium region. The cambium and phloem tissues are especially well 
provided with food which enables the fungus to establish itself outside 
of the xylem ring in the phloem or cortex, from which it readily makes 
its way into the new buds as they are formed in this region. 
The plants that escaped infection in the writer's inoculation experi¬ 
ments appear to be the ones in which the stolon after taking root grew 
on to some extent without forming shoot buds, so no means was afforded 
at that time for the entrance of the fungus into the host. The growing 
tip of a stolon is certainly a very tender structure which one would think 
might be attacked by the parasite. If this happened in any of the ex- 
