DODGE: STUDIES IN THE GENUS GYMNOSPORANGIUM 133 



small plant which I was able to transplant and grow in the greenhouse. 

 In 1915 this small burl bore two sori. The same burl bore six sori in 

 1916. The branch was six years old when cut. The mycelium spreads 

 quite evenly through the cortex and is especially abundant beneath a 

 sorus where we find one or two large haustoria in nearly every cortex 

 cell. The medullary ray cells of the cortex are likewise attacked and 

 the mycelium penetrates down to the cambium. The walls of the 

 tracheids are somewhat thicker than usual, in this respect differing 

 from the specimens examined by Wornle. 



I have been unable to find any intracellular hyphae, and in this 

 six-year-old branch there are certainly no hyphae inside of the cambium 

 ring, that is, in the wood cylinder, such as Harshberger describes. 

 The most striking feature about this fungus is the great abundance 

 of large haustoria found in nearly every cell of the cortex in the 

 vicinity of a sorus. 



GYMNOSPORANGIUM CLAVIPES 



The red cedar may be infected with G. clavipes without difficulty 

 by spraying with aecidiospores. Plowright^ states that it takes two 

 years for G. clavariaeforme to mature sori, but Tubeuf^ found that 

 sori developed one year after inoculation of the juniper. My experi- 

 ence with G. clavipes may serve to explain this discrepancy. 



On August I, 1915, a small cedar was inoculated with Gymno- 

 sporangium clavipes. A few sori appeared in 191 6 on what was, in 

 1915, the growing region of the main stem. In 1917 sori burst out 

 quite generally over the plant. The question has arisen : Is it possible 

 that from the original point of infection of 191 5 the mycelium ran 

 down the main stem out into the branches where further sori formed 

 in 191 7? Inspection showed that the sori were not evenly scattered 

 along the branches, but appeared in groups with intervening spaces 

 of some length between, varying from one to several cm. Serial 

 sections of some of the smaller branches made at points between 

 groups of sori do not show the presence of mycelium. For several 

 inches near the top of the main stem the sori are so close together 

 that mycelium appears to be continuous. It is noteworthy, however, 

 that there are no sori on those parts of the plant that have grown 

 since the plant was inoculated in August, 191 5. The mycelium is 

 intercellular and lies for the most part well out in the cortex just 

 beneath the cork, some hyphal ends even pushing in between the inner 

 cork cells. It may require only one year for full development at the 



* Plowright, C. B. British Uredineae and Ustilagineae. 1893. 

 *Tubcuf, C. MitteJlungen iiber einige Pflanzenkraiilchciten. Zcitschr. 

 Pflanzenkr. 3: 201-205. 1893. 



