212 GRASSES OF IOWA. 



are affected. The plants die prematurely, and soon after death 

 the leaves become torn into shreds. An examination of the 

 affected parts when the variegated linear stripes appear shows 

 a colorless mycelium permeating the tissues of the leaf. In 

 older parts of the leaf blackish masses are clearly made out 

 with the naked eye. These masses consist of the spores and 

 fruiting fungus threads. The erect septate hyphae make their 

 way through the opening of the stoma or break through the 

 epidermis, bearing large three to six-celled spores at the end. 

 Occasionlly one finds these hyphae branched. The mass of 

 brown hyphae and spores along the veins can be seen easily 

 with the naked eye. The spores germinate readily, often a 

 number of germinating tubes coming from a siAgle spore. The 

 Helminthosporium teres, Sacc. , on oats, described by Briosi and 

 Cavara, is closely allied to the above species. The mycelium is 

 intercellular and causes elongated dead spots, finally death of 

 the leaf. 



LEAF BROWNING OF CORN (HELMINTHOSPORIUM TURCICUM, 



PASS.) 



Spot diseases are abundant and destructive on many of our 

 cultivated plants. Corn, so far, has been unusually free from 

 these troublesome diseases. In 1876, Passerini,* an Italian 

 mycologist, described a fungus, Helmintlio&porium turcicum, as 

 occurring on living leaves of corn. It was distributed by 

 Rabenhorst. f 



Earlier, Cooke and EUist described a somewhat similar 

 Helminthosporium, the H. inconspicuum, on dead leaves of corn. 

 The Cooke and Ellis species is sometimes parasitic. Comes§ 

 holds that this fungus is distinct, although closely related to 

 the European. Peck || states that it occurs on living or lan- 

 guishing leaves of Indian corn, and Harvey reports the var. 

 britanicum, Grove on oats. Professor Peck gives the following 

 account of the disease: "If the lower leaves of corn stalks be 

 examined toward the end of summer, some of them will be 

 found to be dead and discolored at and near the pointed end. 

 This discoloration is sometimes continuous, involving the whole 



*La Nebbla del gran turco. Parma. 1876. Abst. J. Schroeter. Just. Bot. Jahr. 

 Just. 1876: 184. 



+Fung. Europ. 23. 



*3accardo. Syll. Fung. 4: 411. Grevillea. 6. f8. Ellis. N. Am. Fung. No. 4.5. 

 SCrittogamia Agraria. 409. 



Ann. Kep. State Mus. Nat. Hist N. Y. 34: 51. 466. pi. 3. b. 

 IIA.nn.Kep. Maine State Coll. 1894: 21. 95. 



