SECTIONAL TRANSACTIONS.— M. 445 



Tuesday, September 15. 



Discussion on Scientific aspects of potato-growing (io.o). 



Mr. H. Bryan. — Some scientific aspects of potato-grozving, with special 

 reference to the health of the seed. 



The main factor in successful potato-growing — provided the land is 

 suitable for potato-growing and is uninfested with potato eelworm— is the 

 use of healthy seed : by that is meant virus-free seed. 



In no industry is so little attention paid to the quality of the raw material 

 used — in this case potatoes planted as seed — and in no industry is the raw 

 material of more importance. 



The greatest benefit scientific research has bestowed on the potato grower 

 is the discovery of the causes of the degeneration of the potato, the realisa- 

 tion that varieties do not perish from senile decay but through contamination 

 with plant viruses, which are spread mainly, if not entirely, by certain 

 species of insects. 



The paper describes how healthy stocks of seed may be maintained in 

 England with consequent increase in crop and reduction in cost of produc- 

 tion. 



Prof. P. A. Murphy.- — Potato viruses and potato production (10.25). 



Prof. R. T. Leiper, F.R.S. — Eelworm diseases of the potato : problems 

 and recent progress (10.50). 



Of the three eelworms known to produce disease in potatoes Heterodera 

 schachtii and Anguillulina dipsaci are now well established and serious pests 

 in Britain. H. marione is at present known only on potatoes from abroad, 

 but the common practice of using exhausted soil from infested tomato 

 greenhouses as garden loam is a potential source of danger to the potato 

 industry. 



H. schachtii and A. dipsaci are spread to new areas by seed potatoes, and 

 administrative control of the sale of seed potatoes from infested lands is 

 urged. The only recognised alternative is insistence on prolonged rotations 

 extending to six years. Recent laboratory experiments suggest that soil 

 infestation with H. schachtii can be greatly reduced, if not completely 

 eradicated, by prematurely hatching the cysts either by chemicals or by the 

 use of root secretions from meadow grasses used in a rotation, or by de- 

 stroying the cysts by using dressings of calcium cyanimide much in excess of 

 those previously suggested. The ' unknown ' factor in ' potato sickness,' 

 presumed to be related to the chemistry of the soil, has recently been shown 

 experimentally by Carroll to be due to the invasion of the first-formed 

 rootlets of the potato by the larvas of H. schachtii. 



Discussion of preceding papers (11. 15). 



Dr.E.WYLLiE Fenton. — Some aspects of man's influence on the vegetation 

 of Scotland (1 1 .45). 



The old vegetation of Scotland and the extensive forests are discussed. 

 Climate may have played some part, but not the most important part, in the 

 destruction of the forests. There is abundant evidence of man's destructive 



