1908] EDGERTON—ANTHRACNOSES 375 



and undisturbed prevents the perithecia from falling out of the leaves. 

 Quite often they grow so large that they push themselves out of the 



leaf. 



The mature perithecium fits exactly Klebahn's description of it. 

 It is subglobose or slightly flattened on the upper and lower sides, and 

 is about 150-200 /ti in diameter. At the upper side it is elongated into 

 a beak, though this is short compared with other forms of Gnomonia. 

 In most cases it is not more than one-fourth to one-third as long as the 



perithecium {jig. 4). 



The asci {jigs. 18, 19) are long clavate, 48-60 X 12-15 z^; generally 

 bent at right angles near the base. Near the apex of the ascus the 

 wall is much thickened and the pore is surrounded by a very refractive 

 ring, appearing under the microscope as two white glistening spots, 

 one on each side of the pore. The ascus is eight-spored, the spores 

 {■fig- 20) being hyaUne, 14-19X4-5/^. straight or slightly arcuate, 

 imevenly two-celled, the upper cell as it is borne in the ascus bemg 

 several times as long as the lower one. 



Still another stage of the fungus is found on the smaU twigs, ^^'hen 

 the leaves fall, all the twigs seem to be perfectly healthy, even to the 

 formation of buds. But toward the last of December and until 

 spring, they begin to show the presence of the disease. The diseased 

 portion, which sometimes extends back several inches from the tip, 

 is covered with the Myxosporium stage. The fungus may live in these 

 diseased twigs for more than a year, producing spores when weather 

 conditions are favorable. ^lost of the twigs remain alive untU 

 spring and start to put out leaves; but when the leaves arc about 

 one-third grown, they quite suddenly wither and die, presentmg the 

 appearance of blight. On badly affected trees a greater part of the 

 leaves die, some large trees being observed ^vhich had only a few green 

 tufts remaining.4 The Myxosporium pustules {jig. 2) are scattered 



4 Since this paper was ^^-rittln, papers by VoN Schrenk (R<-T-^ ^I^- ^ot. Card 

 1907:81-83) and CLINTON (Rep. Conn. Exp. Sta. 1907:360. 1908) ^I'^^^l'' 

 notice, in which it is claimed that the injury to the sycamore in 1907 was due to trost 

 and not to anthracnose. From an almost daily obser^-ation of the trees ^^ Ithaa ^ 

 am convinced that frost had practically nothing to do with the ^^^^^y-J^'J^'^ 

 came on May xx and ax, while the injury developed dunng the firs three we^^;^ 

 June. Furthermore, the blighted twigs were covered with the P^rf-^^-J^^^ ^^;^ 

 sporium pustules, while twigs that were free from the pustules had no blighted Ka.es. 



