262 IOWA ACADEMY OF SCJEXCE Vol. XXV, i:tl8 



mycelium of this is perennial, but infection depends upon 

 meteorological conditions. 



The blackberry and bla^ik cap raspberry rust {Caeomn tiitens 

 Burrill)^'' is coninion in Iowa, and recurs on the same plant year 

 after year, as has been observed for many years. This fact ha.s. 

 of course, been observed by other investig'ators, like Clinton^'' 

 and Newcombe^'. Clinton^^ found the mycelium, especially in 

 the pith, in a more or less zonal area. Neweombe found the 

 mycelium from the stem down to the roots. 



In black knot of plum {Plowrightia morbosa (Schw. ) Farl) 

 the perennial character of the fungus is well known. Where it 

 occurs the disease spreads centrifugally from infected tree-;. 'Che 

 fungus spreads along the diseased stem killing it. Farlow^'' long 

 ago called attention to the perennial nature oif the mycelium. 

 Halsted-° and Humphrey-^ and nearly every AAriter on the sub- 

 ject of black knot has called attention to the perennial character 

 of the mycelium. One of the most etfective ways of destroying 

 the fungus is to remove the infected tree. In a domestic plum 

 orchard under obsen^ation some years ago one variety higldy 

 susceptible was cut out. Since then the disease has not oc'-urred 

 in the orchard. The writer has recently noticed in Osceola and 

 Clarke counties some large trees of PruuHs serotina badly in- 

 fected. Many of the old branches were dead. Sometimes rather 

 large burls are found on the tree, as has been previously noticed 

 in Wisconsin ; whether these are connected with this fungus has 

 not been determined. In some cases perhaps they are. 



G-ymno sporangium glohosum Farlow. The perennial eharaeter 

 of the mycelium of this fungus was described by Farlow--. Pam- 

 meP'*, Thaxter-*, Kern-^ and others. It was observed only once 

 in central Iowa, at Ames. The gall and the part of tlie branch 

 was removed. The fungnis has not been observed since. This 

 fungus is fairly common in southeastern Iowa on Jnnipenis vir- 

 giniana. 



"^This name is used because the writer has not seen the PnccviUi peckiana 

 in Towa, tliougii lie has found it in Wisconsin. Kunkel. Bull. Torrey Bot. 

 Club, JiS, .559-569, hf(s discovered the short and long cvcle foims of Cneoma. 



•"Bull 111. A-'M Kxp. St:i. 29. -'78-296' p'. I-.',. Proc -Am. .\. ul. Art.s & 

 Hci , B. S. 1865-85. See the account of Farlovv also. 



"Joui-. Mycology, a. 106-107. pi. .:.7-"(;. 



"^Bull. 111. Ag-rl. Exp. Sta. 29, p. 277. 



'"Bull. Bussey Institute. Jii'd. 440-453, pi. ',-<;. 



-''New Jersey -Agri. Exp. Sta.. 78. 1-14. 



='Mass. Agrl Exp. Sta.. S, 200-210. pi. J. 

 2=Ampr. IMcmo Boston Soc. Nat. Hist., ...s, .> pi. ISSO. 



-"Bull. Iowa Agrl. Exp. Pta. 84. 10. 



=*BulU Conn. Agrl. Exp. Sta. 107, 1-6. 



"The Nature and Classification of Plant Rust?. Transactions of tie An:eri- 

 can Microscopical Society, .«, 59. 



