MISSOURI BOTANICAL GARDEN. 



the hyphae had passed through the walls. The threads 

 show no preference for the pits. The holes often have the 

 shape of a figure 8, i. e. they enlarge within the secondary 

 lamella, a feature which is common to wood destroyed by 

 many wood-destroying fungi. The scarcity of mycelium is 

 striking, resembling in this respect wood in which Poly- 

 porus sulphureus has been growing.* In branches where 

 the disease is in its youngest stage, the mycelium occurs 

 more plentifully in those areas, which correspond to the 

 holes to be formed later on. Between these areas the 

 hyphae pass, boring through the tangential walls. 



Besides the colorless mycelium, a mycelium is often 

 present in the wood between the decayed holes. This 

 appears to belong to some saprophyte, which has nothing 

 to do with the original decomposition. This mycelium is 

 composed of brown threads which pass through the tan- 

 gential walls preferably and follow the direction of the 

 tracheids up and down. These hyphae form marked at- 

 tachment organs when boring through the cell-walls. Frankf 

 described such organs as formed by the germ tubes of Fusi- 

 cladium tremulae. The hypha when it touches the epidermis 

 forms a swelling with one or more pores, from which fine 

 tubes push through the walls into the epidermal cells. He 

 called the swollen parts " Appressorien " or attachment 

 organs, and believed that they aided the hypha in punctur- 

 ing the wall. De Bary J found similar organs in germ tubes 

 of Peziza Sderotiorum ; these were formed * ' owing to a 

 mechanical stimulus, which the resistance of a solid body 

 exerts on the hyphal branches." Biisgen described the 



* Hartig, R. Zersetzungserscheirmngen des Holzes 110. 



f Frank, B. Uber einige neue u. weniger bekannte Pflanzenkrank- 

 heiten. (Ber. d. deut. bot. Ges. 1 : 30. 1883.) 



% De Bary, A. Uber einige Sclerotinien u. Sclerotienkrankheiten. 

 (Bot. Zeit. 44:377. 1886.) 



Biisgen, M. Uber einige Eigenschaf ten der Keimlinge parasitische 

 Pilze. (Bot. Zg. 51 : 53. 1893.) 

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