DODGE: STUDIES IN THE GENUS GYMNOSPORANGIUM 131 
ciated. Hyphae may sometimes be intercellular. Swollen and 
nodular hyphae are not infrequent. Harshberger questions whether 
haustoria are ever present. It is well known from the work of Hartig 
and others that hyphae of wood-destroying fungi are capable of boring 
through lignified cell walls. Such fungi obtain their nourishment by 
activities leading to the disorganization of wood cells. The rusts are 
highly parasitic and haustoria play an important part in their nutrition. 
It would be interesting to find that such trunk parasites as G. biseptatum 
and G. Ellisii are more like the common heart rot fungi than they are 
like other rusts where the hyphae crowd in between the cells or mass 
in the intercellular spaces. My own observations do not support 
several statements made by Harshberger. 
(GYMNOSPORANGIUM ELLISII 
I have succeeded in infecting Chamaecyparis by spraying potted 
cedars with aecidiospores of G. Ellisii (G. myricatum). Several 
cedars naturally infected and bearing brooms of different ages have 
also been grown in pots, so that I have had an abundance of material 
in all stages of growth for study. 
The sorus usually matures about twenty-one months after inocu- 
lation. Where young leafy branches have been infected we find 
that the sorus may break out either in the leaf axil or through the 
leaf itself. At this time there is very little distortion of the twig. 
The primordium of the axial sorus is partly in the tissue at the base 
of the leaf and partly in the stem cortex beneath. Where the sorus 
emerges through the leaf we find that there is an increase in the 
number of mesophyll cells and the sorus primordium is not far below 
the epidermis. Strands of hyphae can be traced down to the short 
vein and into the woody portion of the stem. Serial sections show 
that the mycelium does not travel up and down the stem very rapidly; 
in some cases only one or two cm. in the first two years. Where a 
rapidly growing main stem is infected the hyphae run as much as 
five cm. in the same time. Trunks thirty years old have been cut 
and one such shows traces of mycelium for a vertical distance of only 
about ten cm., although the fungus had been active during the life 
of the tree, thirty years. Sections taken from various parts of a small 
artificially infected plant bearing a dozen potential witches’ brooms 
show that each broom will be the result of a separate infection. 
The mycelium does not enter at one point and spread through the 
entire plant. However, if the original infection should be at the 
growing point of the main stem a broom is formed that permanently 
dwarfs the plant. The mycelium invades every tissue except the 
cork. It is found in patches in all of the annual rings, and is espe- 
