Lecture on the Parasitic Fiimji of the British Farm. 387 

 as in the drawing. Fig. 8. You may observe the spores in the highly 



P'ig. 8. Uredo rubigo. 



magnified diagram, most accurately drawn from the microscope by 

 Mr. Leonard. They are seen growing on the mycelium, which 

 finds its matrix in the tissues of the plant. There is a curious 

 botanical question whether this uredo passes to puccinia. I think 

 the best evidence confirms the opinion that such is the case. 



(3.) The sooty powder on the flowering parts of corn-plants, 

 called smut, chimney-sweepers, and dust-hrand, is formed of the 

 spores of another uredo, called uredo segetum. It renders the 

 whole interior abortive ; the pedicel of the flower swells, and a 

 black dust occupies the whole. These spores are so diminutive 

 that the diameter of one is only Wto- inch. Strange to say, some 

 farmers welcome its appearance, because they conceive it augurs 

 a good crop, forgetting that whatever ear it attacks, it makes one 

 less in that crop. 



(4.) Another uredo, called hunt, or pepper-hrand, seizes on the 

 grain of wheat, and that to a great extent if not guarded against. 

 This uredo is termed uredo fetida, on account of its filthy odour. 

 If you break a grain of wheat infected, you will find the flour 

 replaced by a black mass, oily and fetid, and all the ovary is seen 

 to be destroyed, except the integument, which swells and encloses 

 the spores, amounting in a single grain to nearly four millions. 



They are, like those of 

 Jka, _ s\^-:^ .<<^^^ \iK -a:^ uredo rubigo, shown in 



Fig. 9, on their myce- 

 lium or spawn, and are in 

 diameter about -^^ inch. 

 This drawing, also from 

 the pencil of Mr. Leonard, 

 shows the spores perfectly 

 as they would appear un- 

 der an achromatic of yV 

 inch focal length, with, an 

 Uredo fetida. eyc-picce of moderate 



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