88 THE VICTORIAN NATURALIST. 



also cause fermentation in suitable nutrients. This is one reason 

 for rotation of crops, as by changing the host-plant the spore of the 

 disease-plant cannot live the next season on the new host-plant. 

 If a spore of the wheat rust plant is sown with the wheat seed, 

 and obtains a suitable amount of moisture and heat for its 

 wants, but not sufficient to start the wheat seed into growth, 

 the rust spore vegetates, and not finding the wheat plant ready 

 for it, dies, and it then actually feeds instead of injuring the 

 young wheat plant ; so wheat seed from a field which has suffered 

 from rust sometimes produces actually a crop free from disease. 

 The slimy disease of potatoes also causes fermentation, but at 

 this I have not worked much, but have seen sufiicient to see in it 

 a great source of animal diseases. As these so-called lower 

 orders of plant life play such an active part in preparing food 

 for the higher plants, we can only call these rusts or slimy 

 diseases weeds when they are misplaced plants. Many common 

 plants belonging to the Compositse, such as the daisy, flat 

 weed, &c., are liable to fungus disease, and offer a large 

 field for work. 



If thick stems of roses (brambles), chopped short (not too 

 woody, a mistake made by the writer of this paper, using rotting 

 — not rotted — wood as a fertilizer), are placed in the ground 

 down too deep for ordinary cultivation to reach them, they form 

 a source of good to the plants growing over them for many years. 

 There is no doubt much of our scrub could be used advan- 

 tageously in the same manner, instead of, as happened around 

 the house where this was written (Drouin), last autumn, when 

 quantities of plants, full of good oils, flamed around in all the 

 grandeur and beauty of a forest fire, even appreciated in spite of 

 the dread feelings it engendered. Grass seed quickly sovm after 

 these bush fires starts rapidly, as the fires bring up moisture from 

 beneath, but also leaving it drier; they are often followed by light 

 showers, seemingly attracted by the smoke ; but, though six 

 months ago, the hills before the window are black, and only the 

 strongly protected seeds, or the lightly blown seeds from unburnt 

 places, and the mosses, which prefer carbon, are starting into 

 growth with the warmth of spring (August), and the waste of 

 burning is written on the page of Nature. Though these fires 

 consume much that is valuable, the result — -wood ashes — are a 

 most serviceable fertilizer on a farm. They can also be very 

 profitably used, either there or on board of a ship where there 

 are stock, in the feeding of pigs, horses, and fowls, but must be 

 kept dry and clean for this purpose. Fire, of course, cleanses 

 the land from objectionable animal and plant life as well as 

 destroying useful life. 



Many of the diseases of our fruit trees and vines are plants 

 which cause fermentation — yeasts belong to these ; and the well- 



