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. Juniperinum 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; ‘“‘Schlafende 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 W6érnle was dealing with at least 
two species, but the accuracy of Wérnle’s observations is not ques- 
tioned. 
The mycelium of G. clavariaeforme, according to Wo6rnle, 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 
2 Wornle, P. Anatomische Untersuchung der durch Gymnosporangium-Arten 
hervorgerufenen Missbildungen. Forst. Nat. Zeits. 3: 68-84, 129-172. 1894. 
5Fischer, E. Studien zur Biologie von Gymnosporangium juniperinum. 
Zeits. Bot. 1: 683-714. f. I-8. 1909; 2: 753-764. I9I0. 
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