GRASSES OP IOWA. 205 



to botanists, but it is only within recent years, when vegetable 

 pathologists have begun to enquire carefully into the causes of 

 the various diseases of useful plants, that both the Clados- 

 porium and the Sep'oria have been found to be serious pests in 

 the graiofield." 



This fungus disease is common to many grasses and is quite 

 destruclive at times. It was described by Desmasier*. It is 

 CDmmon, not only in this country but in Europe as well. 

 Erikssonf reports it as common in Sweden and CavaraJ says 

 it is on the increase in Italy. Cobb§ remarks on its c )mmon 

 occurrence in Australia. Tielease|| discussed it in his work on 

 fungi injurious to grasses and clovers. It is most injurious to 

 wheat and here it causes the young plant to turn a yellowish- 

 green, then becomes yellow. The leaf finally dries and withers. 

 It appears on the sheaths and culms. The interior of the plant 

 contains an abundance of tha mycelium. la the dead spots 

 of the leaf may be seen small black specks— the periihecia, 

 which are either aggregated or scattered. These perithecia 

 contain hundreds of small, several-celled spores, 40-50'' x 1- 

 15". They are said by Cavara not to be divided. The sporea 

 are, however, occasionally two celled. 



In a somewhat extended account of this disease Cobb states 

 that the entire plant is not always involved. It is a variable 

 fungus, its character depending upon the host which it attacks. 

 On Poa (innuus the leaf is mainly involved and in many cases is 

 totally destroyed. Cavara*^ states that the spots on the leaves 

 are small, elliptical, red or yellow, or the latter may be entirely 

 absent. The injury it does to the young plant is very great; 

 in some cases their total destruction has been observed. 



Janczewski** who has studied the life history of Septoria 

 graminum states that this represents the pj?cnidial stage of 

 Leptosphaeria tritici and that the conidial form is the Clados- 

 porhcm herbarum. 



*Ann. Sci. Nat. Bot. II. 19: 339. 1843. 



+Erlksson. On nagra sjukdom'ir a odlof vaxter samt om atgarder till motarbet- 

 ande af vaxtsjukdomar. 20. 



Tabeuf. Pflmzenkrankheiten. 491. Mangin also states that It Is parasitic. See 

 Jour. Roy. Mic. Soc. 1898: 568. 



Loverdo. Les maladies crypt. 283. 



iZelt f. Pflanzenk. 3: 19. Also Briozi. Zelt. f. Pflanzenk. 3: 216. 



S Plant diseases and their treatment. Agrl. Gaz. New So. Wales. 3: 991. 



Illn Beal Grasses of No. Am. 1: 428. 



tl. c. Zeltsch. f. Pflanzenk. 3: 19. 



**Bull. Acad. d. Sc. Cracovie 1892: See Frank Krankheiten. d. Pflanzen. 302. 419. /. 63. 



