POTATO-FUN GTJS. 105 



" Eetrospective Review," 1820-26. He never pointed out to me the 

 articles from his pen, but from internal evidence I liave no doubt 

 that those on Ray and Lister, and on various early and little-known 

 travellers, -were written by him. They show that long before he 

 became associated with Mr. Brown he had a strong love for natural 

 history, and had acquired habits of careful and exhaustive research. 



William Caeeuthers. 



RESEARCHES INTO THE NATURE OF THE POTATO- 

 FUNGUS, PHYTOPHTEORA INFESTANS. 



By Professor A. de Baey, of the University of Strasbourg. 



IjSTTRODUCTIOSr. 



Peeviofs to my undertaking, at the request of the Royal Agricul- 

 tural Society, the task of endeavouring to extend our knowledge of the 

 life-history of the Potato-fungus, I had devoted a long series of re- 

 searches to this subject. Although I assume that those researches, so 

 far as they have been published, are known, and in fact" I must do so 

 for the sake of avoiding too great minuteness of detail, yet a short 

 resume appears indispensable ; and I will give it by way of intro- 

 duction, referring, at the same time, to the existing literature of the 

 subject.* 



1. The Potato-fungus is usually classed with a small family of 

 parasitic Fungi, which since 1863 has been known as the PeronosporecB. 

 Taking first the purely morphological peculiarities of these Fungi, 

 without regard to their immediate adaptation to the medium in which 

 they grow, we find in the first place that the growing plant {thallus, 

 mycelium) consists of densely ramified tubes ; these are full of proto- 

 plasm, and continuous, or without septa, except that some species, 

 especially when they are old, have irregular septa. Some small 

 branches of the mycelium are specially developed as organs for attach- 

 ment and as suckers ; others produce the organs of reproduction. One 

 set of these bear non-sexual cells {conidia), and are therefore called 

 " conidia-bearing " {conidiophores) ; others, which mark the complete 

 development, form at their tips the sexual organs : these are (first) 

 the bladder-shaped female cells (oo^onm), from the protoplasm of which 

 a thick-walled oospore is produced after fertilisation by (second) the 

 small male cells {antheridia). From the germinating oospore springs 



* " Becherches sur le developpement de quelques champignons parasites," 

 Ann. Sc. Nat. 4"><' serie, t. xx. "Die gegenwartig herrschende Kartoffelkran- 

 keit," Leipzig, 1861. " Zur Kenntniss der Peronosporen," De Bary & 

 Woronin, Beitr, z. Morphol. &c. d. Pilze, heft 2, p. 35. 



