PARASITIC FUNGI. 293 



tL.e question as to their origin ; and he concludes that 

 endophytes are not produced from the metamorphosed 

 substance of diseased plants, but that they originate from 

 germs which penetrate healthy plants and develop a 

 mycelium. In the course of his investigations he notices 

 the occurrence in the genus Cystopus of organs similar to 

 t'lose long since discovered by Tulasne in Peronospora^ 

 which have been called Oogonia. He observes that rami- 

 lications perform the functions of antheridia, or male 

 organs; and he proceeds to describe the production by the 

 oospores (or impregnated contents of the oogonia) of active 

 zoospores, similar to those produced by the ordinary spores 

 of Cystopus. Dr. De Bary states that these zoospores, after 

 remaining active for three or four hours, lose their cilia and 

 power of motion, assume a ceHulose covering, and ger- 

 minate. He adds that the germ-filaments enter readily 

 by the stomates and leaves of the nutrient plant, but that 

 those hlaments only become developed which enter the 

 stomates of cotyledons. In Peronospora the development 

 of the antheridia, oogonia, and oospores is said by De Bary 

 to be the same as in Cystopus ; and he gives particulars of 

 the mode of germination of the conidia, and remarks on 

 the growth of the parasite, which will be more profitably 

 studied in the paper itself 



Parasitic fungi, vegetable blights as they are commonly 

 called, have of late years become objects of earnest atten- 

 tion, on account both of the enormous damage done to our 

 growing crops, and also of the many curious facts in their 

 history which have been brought to light. Corn-blights 

 consist chiefly of mildew, Puccinia^ smut, bunt, rust, or 

 red-robin, Uredo. Oidium is a common mildew ; Bo- 

 trytis another ; jEcidium forms a kind of rust infecting 

 pear-trees, the peridia of which form a very pretty object 

 for the microscope. (Plate I. No. 22, jEcidium Berbsridis.) 

 In the full-grown condition they appear as little cups filled 

 with reddish-brown powder (spores), and may be detected in 

 their earliest stages by the deformities they produce in the 

 structure of the plants infested, or by pale or reddish spots 

 on the green surface, arising from the presence of the 

 fungus beneath. They are common on the coltsfoot, the 

 berberry, gooseberry, buckthorn, nettle, &c. Plate I. 'So. 19, 



