UREDO. 



ripe it occupies the whole interior of 

 the grain, but does not burst the skin, 

 so that the grain retains the charac- 

 ter of being perfectly sound. The 

 sporidia are frequently mixed with 

 delicate fibres, which seem to consti- 

 tute the niycelia of the plant. Hens- 

 low calculates that a single grain 

 of wheat may contain more than 

 4,000,000 of sporidia. Each of these 

 sporidia probably contains millions 

 of sporules ; hence some idea may 

 be formed of their minuteness, as 

 well as their capacity for spreading 

 themselves in every direction. An- 

 other peculiarity of this fungus is, 

 that it has a very disgusting smell, 

 and the consequence is that flour 

 made from grains containing it can- 

 not be eaten. Flour thus spoiled is, 

 however, sold to gingerbread-makers, 

 who have found out that mixing it 

 with treacle conceals its disagreeable 

 odour. It does not appear to act in- 

 juriously when taken. In raising 

 wheat for seed, the greatest care 

 should be taken that none affected 

 with the smut fungus is used, as it 

 seems proved that where the sporules 

 of the fungus are present in the seed 

 sown, they will grow up with the 

 plant, and be developed at the period 

 of its ripening the fruit. Many rem- 

 edies have been proposed for getting 

 rid of the sporules from wheat about 

 to be sown. Washing with clean 

 water has been found effectual, and 

 with lime-water much more so, but 

 of all applications a solution of sul- 

 phate of copper (blue vitriol) seems 

 to answer best. The following is a 

 good instance of the effect of dress- 

 ing wheat : ' Mr. John Woolnough, 

 of Boyton, sowed a large field in al- 

 ternate breadths with wheat taken 

 from a good sample without dressing, 

 anri wheat that had been dressed. 

 Long before the grain was ripe the 

 difference was most distinguishable. 

 Upon those stretches sown with 

 dressed wheat it was difficult to find 

 any branded ears, while the others 

 were so branded as to make him de- 

 termine to carry the wheat at sep- 

 arate times to different places.' " — 

 (Linn. Trans., vol. v.) 



The common character of the fun- 



Fig. 1. 



gi of this class 

 is their production 

 within the plant, 

 through the skin 

 of which they oft- 

 en break, as in the 

 Urcdo diffusa, that 

 attacks fruit-trees 

 {Fig. 1). 



" Urcdo ruhigo 

 and linearis form 

 yellow and brown 

 oval spots, and 

 l)lotches of an or- 

 ange and yellow 

 colour upon the 

 stem, leaf, and chaff of grain, and va- 

 rious grasses. The sporidia of U. 

 linearis are more oblong than those 

 of U. ruhigo, but they are frequently 

 found together. When these plants 

 are present the disease of the grain 

 is called rust, red rag, red robin, 

 and red gum. This is the plant 

 which Henslow believes to be iden- 

 tical with the Puccinia graminis, 

 which occurs in wheat affected with 

 mildew." Figure 2 represents the 

 Fig. 2. 

 ^hi h. 



Puccinia graminis, OT rust: it is of the 

 natural size in the stem, a, magnified 

 in I), and the stem also magnified in c. 

 " The mildew and the rust are oftea 

 confounded together by farmers, and, 

 as shown by Henslow, there is no 

 difference in the essential character 

 of the plant which is the offspring of 

 the disease. Rust and mildew are 



819 



