SOD CASUALTIES OF VEGETABLES. CHAP. 



the leaf, and thus preventing the access of atmos* 

 pheric air.* 



Examples. Sometimes the disease is occasioned by an extra- 

 vasation of juices which coagulate on the surface of 

 the stalk so as to form a sort of crust, investing it as 

 a sheath, and preventing its further expansion. On 

 the 7th of July, 1 8 1 6, 1 observed some stalks of a Grass 

 partly enveloped with a crust, not unlike a piece of 

 dried orange-peel, particularly when viewed through 

 the microscope ; the part thus enveloped proved to 

 be that in which the spike was yet contained within its 

 sheathing leaves. The crust which thus totally locked 

 up and suffocated the spike extended from about If 

 to two inches in length, surmounted by the terminat- 

 ing leaf whose base it also invested, and thus 

 giving to the Grass the appearance of a Typha in 

 miniature. 



On examining the crust more minutely it seemed 

 to consist of thousands of yellowish globules imbed- 

 ded in a sort of ground resembling mortar. But in 

 some species the crust was much paler, and not 

 unlike the Boletus Medullapanis in a recent state. It 

 not only invested the outer leaf, but also the inner 

 leaf though sheathed by the outer, and the spike 

 though sheathed by the inner leaf. The ear was so 

 totally consumed or so imperfectly formed that 

 I could not yet ascertain what Grass it was. But 

 it had the habit of Holcus lanatus, which, by 



* Willdenow, p. 350. 



