14 Transactions. 



%id of December. 



Major BuWDEN, Vice-President in the chair. Twenty-six 

 members present. 



Nciv Member. — Mr John A. Moodie, Solicitor. 



Donations. — Mr Eobert Thomson, Joiner, presented, through 

 Mr James Barbour, the dove carved in wood and gilt which 

 formerly stood over the canopy of the New Church, Dumfries 

 (Greyfriars'). When that church was taken down the dove was 

 purchased by the late Rev. Dr M'Farlane and placed by him over 

 his pulpit in Troqueer Chui"ch, which has lately been rebuilt. 

 This interesting relic came into the possession of the contractor, 

 Mr Thomson. Mr James M'Andrew presented Juncus tenuis and 

 Rhyncospora fusca found by him in the district and now first 

 recorded. Fifteen new rules were adopted, on the motion of Mr 

 J. Wilson, the Secretary. 



Communications. 



I. Certain Common Parasitic Fungi. By Mr George F. Scott- 

 Elliot, M.A., F.L.S. 



The fungus {Pero)iospora in/estans )t\\At causes the well-known 

 potato disease consists of a delicate series of branching filaments 

 that penetrate between the cells of the potato leaf and suck from 

 them the materials that should feed it. By this procedure the 

 potato leaf decays, and this causes the unpleasant odour that is 

 one of the signs of the disease. The fungus is enabled to spread 

 from one potato plant to anothei by means of conidiospores. 

 These are formed on the under surface of the leaf (giving rise 

 to a sort of whitish bloom) on the extremities of a branched 

 filament which is protruded through a stoma. The conidiospores 

 are blown by the wind on to the upper surface of a potato leaf, or 

 in some cases on an exposed tuber. If the weather happens to be 

 wet, the conidiospores break up into 7 or 8 little " swarm spores," 

 and these penetrate (in the case of the leaf) through the cuticle, 

 and by germination produce a new series of filaments in it. 

 (In the case of the tuber, the fungus makes its entrance by the 

 " eye.") Towards the end of the autumn the fungus makes its 

 way down the stalk to the tubers, and passes the winter in a latent 

 condition in them. When the tuber germinates in spring the 

 fungus grows, keeping pace with the growth of the young plant, 

 which is thus doomed from its earliest days. A special kind of 



