DODGE: STUDIES IN THE GENUS GYMNOSPORANGIUM 129 



lie at some distance. Farlow noted that the hyphae of this species are 

 exceptionally large and that the brown mycelium runs down into the 

 wood and along the medullary rays and also makes other brown 

 patches extending some distance in circular areas between the annual 

 rings. The greater part of the mycelium is found near the cambium 

 and large masses of it are collected at points in the bark in prepara- 

 tion for the formation of sori. 



Wornle^ made an extensive study of the relationships of host and 

 parasite in nine species, and his report published in a forestry 

 journal furnishes a valuable contribution on the subject. He en- 

 deavored to determine the particular tissues with which the mycelia 

 are associated and stated his conclusions with considerable positive- 

 ness. G. Juniperiniim was of special interest to him inasmuch as he 

 supposed that the sori found on leaves as well as those on small twigs 

 belong to the species that produces larger sori on the main stems. He 

 could see that the mycelium in an infected leaf was connected with 

 that from a small twig. He also learned that the leaf form is per- 

 ennial. Four successive cork callus formations were found in one 

 case, showing that for four years a sorus had been developed at the 

 same point on the leaf. In the stem-inhabiting type he found that 

 the mycelium is present in the wood as well as in the bast and cortex. 

 Radially placed strands of parenchyma accompanied by mycelium 

 are common in the wood ; ' ' Schlaf ende Augen ' ' he calls them . Hyphae 

 are intercellular, and he noted in some cases the presence of haustoria. 

 Although Wornle was not himself clear regarding the relationship of 

 the three forms of the rust which he called G. Juniperinum, he was 

 inclined to believe that the fungus gains entrance through the leaves, 

 the mycelium later running down the twigs and into the main 

 stem, where it becomes firmly established. Fischer^ has shown that 

 this was a false assumption since Wornle was dealing with at least 

 two species, but the accuracy of Wornle's observations is not ques- 

 tioned. 



The mycelium of G. clavariaeforme, according to Wornle, is not 

 present in the wood, although considerable transformation of tracheid 

 tissue is to be seen in infected stems; arcs and sectors of this 

 tissue are replaced by parenchymatous cells. He found, however, 

 no mycelium in such areas. As the mycelium is generally distributed 

 in the cortex and bast, he assumes that the cambium is in some way 

 stimulated to develop more than a normal amount of wood cells, some 



^ Wornle, P. Anatomische Untersuchung der durch Gymnosporangium-Arten 

 hervorgerufenen Missbildungen. Forst. Nat. Zeits. 3: 68-84, 129-172. 1894. 



^Fischer, E. Studicn zur Biologic von Gymnosporangium juniperinum. 

 Zeits. Bot. i: 683-714./. 1-8. 1909; 2: 753-764. 1910. 



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