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from the face of the earth. They are essentially scavenger plants. The 

 two tribes into which they may be divided have separate tasks assigned 

 to them in the grand scheme of creation. The office of one is obviously 

 to hasten the decay of matter already decaying. The office of the other, 

 I believe is to hasten the death of that which is unhealthy. Those which 

 flourish on dead organic matter appear only when decay has commenced, 

 a, fact well known to most. "Fungi," says Mr. Solly, "are only devel- 

 oped in those solutions which are in that state of putrefaction favorable 

 to their growth ; moreover they do not appear till the solution has acquired 

 that stale." There must, I believe, be unhealthy action, possibly some 

 slight chemical change in the fluids of superior plants before parasitic 

 fungi can successfully attack and destroy them. Is this view of the case 

 then supported by facts ? Is the state of the superior plant consequent 

 on certain atmospheric or other influences, the condition requisite for the 

 attatck of the parasite, or does the growth of the parasite depend on cer- 

 tain atmospheric conditions only ? There can be no doubt whatever that 

 the state of the weather has considerable influence on the development 

 and increase of parasitic fungi in ordinary cases. In moist dull seasons, 

 crops are observed to be always more or less aff'ected by mildew. Any 

 sudden check in the progress of vegetation, such as is caused when hot 

 sunny weather is succeeded by calm, dull, foggy days, or by a sudden 

 transition from weather favorable to rapid growth to weather cold and 

 wet, is generally considered to be the precursor of blight and favorable 

 to the fjrowth of funiri. 



Now, circumstances like these would exercise an injurious influence on 

 the health of the larger plants ; it is therefore doubtful whether it is not 

 the state of the plant attacked rather than any peculiar atmospheric con- 

 dition which favors the growth of the parasite. Other facts seem to indi- 

 cate very clearly that circumstances of soil, situation, manure, &c., pre- 

 dispose plants to an attack of fungi independent of atmospheric influen- 

 ces. Almost all our cultivated crops are known to have their peculiar 

 parasites. "In favorable seasons," Mr. Berkeley observes, "the fungi 

 which infest grain crops are not developed ; in unfavorable seasons thejr 

 spread like wild-fire." Since the appearance of the potatoe blight hare 

 the seasons been favorable to the growth of fungi or otherwise ? Were 

 grain and other field crops universally, or to any considerable or unusual 

 extent attacked ? It is well known this has not been the case. Then 

 comes the puzzling question — if this universal attack on the potato© be 

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