CETRARIA 



219 



the slow fermentation of the soaked and ground lichen in the presence of am- 

 monium a,nd potassium carbonates. A red colour is first produced which gradually 

 changes to blue. The blue liquid is drawn off and 

 evaporated, with the addition of chalk and gypsum ; 

 the mass is then cut into small rectangular cakes and 

 dried. The chief constituents are erythrolitmin and 

 azolitmin, together with erythrolein and spaniolit- 

 min. The lichens themselves contain lecanoric acid, 

 erythrin and orcin. By the action of alkalies, these 

 yield orsellinic acid. Orsellinic acid by further change 

 yields orsin, from which, by oxidation in the presence 

 of ammonia the colouring matters are produced. 



Cudbear (Persio) is a reddish colouring matter 

 prepared by an analogous method from the same 

 lichens. 



" ERGOT 



Source, &c. Ergot is the sclerotium of 

 Claviceps purpurea, Tulasne, (N.O. Pyreno- 

 mycetes) originating in the ovary of the rye, 

 Secdle ceredle, Linne (N.O. Graminece). 



In the spring or early summer the spores 

 of Claviceps purpurea are carried by the wind 

 on to the flowers of various Graminaceous 

 plants, in the case under consideration on to 

 those of the rye. Here they germinate and 

 produce colourless hyphse, which envelop, with 

 the exception of the apex, the very young 

 ovary, and penetrate the outer part of the 

 pericarp, covering it with a soft white felted 

 mass, which gradually takes the place of the 

 ovary, and is known as the sphacelia. During 

 this period a saccharine secretion, ' honeydew,' 

 is produced by the hyphse, and at the same 

 time numbers of conidia are formed, thus 

 contributing^ to the further dissemination of 

 the fungus by means of the insects attracted 

 to the honeydew, a small weevil which feeds 

 on the saccharine secretion being especially 

 active. After the felted mass has reached its 

 full development, the sclerotium is gradually 

 produced at its base by the hyphse forming 

 a dense compact mass instead of a loose felt. 

 The sclerotium grows and finally projects from FIG. 115. Ear of Eye 

 the ear of rye (which has by this time ripened), J3^^ 

 bearing on its apex the remains of the felt. Natural size. (Luer- 



In this compact form the fungus is able to ssen.) 



