280 Journal of Agricultural Research, voi.xx, no. 4 



6. A fine commercial strain of the variety Pearl, grown at Crandon, 

 Wis., in 1914 and reported to be free from wilt, leafroll, and similar 

 diseases. 



7. Wisconsin certified seed potatoes, variety Pearl, secured from the 

 grower. 



8. Culls from two lots of Maine-grown stock of the variety Pearl. 

 One of these lots was reported healthy and the other as diseased with 

 leafroll. There was no difference in the performance of the two lots in 

 either locality where they were grown, and disease was absent. They 

 are therefore grouped together as healthy. 



9. Certified seed potatoes of the variety Rural New Yorker, grown at 

 Boss Lake, Wis. A second lot of similar, though uncertified, material 

 of the same variety but from another grower near Racine, Wis. 



10. A small lot of Wisconsin-grown stock of the variety Pearl, com- 

 posed of tubers on the stolons of which Colletotrichum pycnidia were 

 developing. 



1 1 . Four so-called types of commercial stock of the variety Rural New 

 Yorker, supplied by a local grower of Greeley, Colo., who had used his 

 own home-grown seed for a series of years. These types were really only 

 rather imperfectly established size grades, evidently obtained by bin 

 selection from the general field run of his stock. 



C. — Parasitic disease group. 



12. The progeny of representative hills from a typical "Fusarium- 

 blight" field of the variety Early Ohio, grown at Greeley, Colo., in 1914, 

 dug in August and stored in a mass lot. 



13. Ten hill lots of the variety Early Ohio, grown at Greeley, Colo., 

 in 1914. The physical condition of the soil of the field was poor, and the 

 plants were small and dwarfed. 



14. A representative lot from a field of choice stock of the variety 

 Sir Walter Raleigh, grown in 191 4 on a field at East Lansing, Mich., 

 which was heavily infected by Fusarium. Every plant in the field, with 

 the exception of about one-quarter of 1 per cent, wilted and died three 

 or four weeks before frost. 



15. Sixty-one hill lots of the variety Pearl, grown in Wisconsin in 1914. 

 The hills selected were from vines with more or less rolled foliage and a 

 brown discoloration of the vascular tissue of the stems. Cultures from 

 the discolored stem tissue failed to yield Fusarium. 



16. Eighteen hill lots of the variety Pearl, grown from Wisconsin seed 

 at Greeley, Colo., in 1914. Cultural tests at digging time showed unusual 

 infection of the vines with Fusarium oxysporum. 



17. Six hill lots of the variety Red McClure, grown at Greeley, Colo., 

 in 1 914 on vines shown by isolations to be infected with Fusarium 

 oxysporum. 



