BLIGHT OF WHEAT. 43 



Wheat, the leaves of Roses, Blackberry, Potentilla, Box, 

 and Ground-ivy. We merely see small black spots, usually 

 surrounded by a circle of orange-coloured cells, which if we 

 scrape off and soak for a minute either in turpentine or 

 diluted nitric acid, each particle of black dust (for it appears 

 nothing more to the naked eye) is found to be a pear- 

 shaped seed-vessel, divided into compartments containing 

 spores. This Puccinia of the Rose or Blackberry has from 

 five to seven compartments, or spore-chambers, and is the 

 best specimen to collect for observation. Some botanists 

 call it Phragmidium, and Aregma. 



If you wish to see the actual escape of 'the spore, scrape 

 the fungus from the leaf, and let it soak in a little alcohol 

 on the slide to disperse the air. Before the spirit has 

 quite evaporated, add a drop of nitric acid under the thin 

 glass cover, and warm it over a spirit-lamp, press the glass 

 gently, and in all probability the inner cell of the spore- 

 case will come out, enclosing the spore itself. 



To see the germination of Puccinia, you have only to 

 scatter some of these spore-cases in the spring on some 

 moist flannel, or on a floating piece of cork, when they will 

 presently throw out long colourless filaments, at the end of 

 which three or four septa will be seen filled with orange- 

 coloured endochrome or pulp of granular matter ; then a 

 spicule will rise on each septum, 'and expand into a globular 

 head, into which the orange-coloured matter will pass, and 

 these eventually fall off and begin to germinate on their 

 own account. 



The spores of fungi, being light and excessively minute, 

 float in the air, enter plants through the stomata, and ger- 

 minate in the cell beneath. 



BLIGHT OF WHEAT (SMUT) . 



This is a fungus of globular form, black and powdery, 

 covering the young ears of corn like a coating of soot. It 

 is called Uredo segetum. The spores are so exceedingly 

 minute, that upwards of seven millions eight hundred and 

 forty thousand of them would be required to cover a square 

 inch of surface. 



