DODGE: STUDIES IN THE GENUS GYMNOSPORANGIUM 131 



dated. 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 Chamaecy parts by spraying potted 

 cedars with aecidiospores of G. ^llisii {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- 



