: 
; 
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1876.] Botany. 369 
has the power of torsion in drying, possessed by the cells, been hitherto 
shown to be of use in the economy of any plant. — A. W. BENNETT. 
Tur Poraro Disease. — The supposed discovery of the sexual re- 
productive organs of Peronospora infestans, the fungus which causes the 
potato-blight, by Mr. W. G. Smith, continues to attract much atten- 
tion in England and on the Continent of Europe. The eminent my- 
cologist, Professor De Bary, of Strasburg, does not altogether accept 
Mr. Smith’s conclusions, believing that what he considers the resting- 
spores of Peronospora must belong to some other fungus accidentally 
present in the decaying tissue; and his views were recently explained 
at the Linnean Society of London by Mr. Carruthers, F. R. S$. Pro- 
fessor De Bary proposes to divide the group Peronosporee into three 
genera. In Cystopus the conidiophores grow in large bunches, the conidia 
being developed in single rows in basipetal order. In Peronospora, from 
a tree-like mycelium, conidiophores arise singly or in small bunches at 
the ends of the branches, and have no successors in the direct line. The 
hew genus, Phytophthora, to which the old Peronospora infestans be- 
longs, differs in its multiple and successive conidia, which, when shed, 
leave swellings on the branches. In all three genera the ripe conidia, 
when placed in water, produce ciliated zodspores, which penetrate the 
tissue of the host and develop threads or mycelium. By another and 
sexual mode of propagation the odgonia, bladder-shaped female cells, 
after being fertilized by the small male cells or antheridia, produce from 
their protoplasm a thick-walled odspore, from which mycelial threads 
Sprout, and the process is then repeated. A considerable period of in- 
activity may, however, precede the germination of the odspore, which 
în this case hibernates during the winter, while its host decays. The 
conidia propagate and spread the fungus during the summer season only, 
and do not live through the winter. Professor De Bary has found in 
decaying potato-tubers bodies exactly corresponding to odgonia. On 
experimenting with the odspores of these and planting them in potato- 
Plants he obtained minute bodies’ which conducted themselves precisely 
like z00spores, and in most respects resembled those of Pythium. Other 
*xperiments with them, on the moistened legs of dead flies and bodies of 
mites, resulted in their complete phases of development which were 
watched step by step, the zodspores producing a plentiful crop of myce- 
Hum, ete. - As'this new fungus differs in many ways from Phytophthora 
mfestans, De Bary proposes to call it Pythium vexans, and he regards it 
m belonging to the Saprolegnieæ. The fungus named by Montagne 
Artotrogus, and the warty bodies found associated with it he believes to 
H two forms not connected genetically, and only imperfectly known. 
€ has likewise investigated the question of the perennial mycelium of 
ophthora occasionally hibernating where the oöspores are not found in 
sa dia trict, and believes that he has proved that there are two methods 
Which the conidia may pass from the tuber to the foliage. — A. W. B. 
VoL, x. 20. 6. 24 
