NOTES AND ABSTEACTS. 



387 



blackening of the vascular tissue to a depth of about ^ inch; which 

 later may spread throughout the tuber. In some cases the discolora- 

 tion appears in patches, and these patches should be cut out of the 

 seed tubers before planting. Badly discoloured tubers should never be 

 used for seed. 



The symptoms in the field are slow early growth, apparent cessa- 

 tion of growth when plants are from 10-15 inches high, accompanied 

 by general yellowing of the foliage, the inward rolling of the leaves, 

 and general wilting on the first hot days, and the early maturity of 

 the plant, which finally turns yellow and dies, but the stem remains 

 as a rule erect. 



On cutting across the stem and roots the vascular system shows 

 discoloration. 



Two other potato diseases are mentioned with which the Fusarium 

 blight may be confused, namely (i) Internal blotch causing rusty, 

 irregularly distributed blotches in the flesh of the tubers, but no external 

 symptoms. No organism has as yet been found causing this blotch. 



(ii) Black-leg — a bacterial disease of stem and root. 



Blackened lesions appear on the stem, and the rapid decay of the 

 sh£^nks causes wilt. But it may be distinguished from Fusarium by 

 the absence of the characteristic yellowing of the foliage which always 

 occurs in cases of dry rot. 



The remedies suggested are : 



1. Sowing Fusarium-sick soil with grain or grass and not growing 

 potatos on that soil for at least six years. 



2. Seed treatment (a) by dipping for 1-2 hours in solution of 1 lb. 

 of commercial 40 per cent, formalin to 30 gallons of water, (b) Fumi- 

 gation of seed with 3 lb. formalin; 23 oz. potassium permanganate. 



The above quantity is enough to treat 1000 cubic feet of space 

 occupied by crates and trays. 



3. The cutting away of diseased patches from seed tubers. 



4. Careful destruction of diseased branches and refuse. 

 Good plates are given.— D. M. C. 



Prairie Grove, An Isolated. By H. A. Gleason (Bot. Gaz. 



pp. 38-49, Jan. 1912; 2 figs.).— This isolated wood. Bur Oak Grove, 

 is near the village of Eoyal in Champaign county, Central Illinois. It 

 is surrounded on all sides by level prairie, but covers a number of 

 elevations and depressions of irregular shape and about ten feet in depth. 

 Near the south end of the grove the forest is open with " blue grass, " 

 and consists chiefly of Quercus imhricaria, Q. velutina and Carya spp. 

 In the middle of the grove Q. macrocarpa {some trees three to four feet 

 in diameter) is most important, with Juglans, Ulmus, Celtis, Gleditschia 

 triacanthos, &c. In the northern end Q. rubra and Tilia americana 

 appear. Here also there is a conspicuous deposit of leaf -mould, and a 

 denser shade with an abundant herbaceous vegetation. 



The forest occurs only on the ridges and at about two feet above 

 the former maximum level of standmg water in the depressions (these 



