218 TRANSACTIONS OF THE ILLINOIS 



evidence of fungi make their appearance, while under other circumstan- 

 ces the reverse may be true. But a greater source of difference of opinion 

 comes from the want of fully understanding the habits and laws of growth 

 in general of both kinds of plants, the afflicted and the afflicting, and in 

 particular the special habits and laws of growth of the individual species 

 concerned. As an illustration from the animal world we may take two 

 snakes that look very much alike, and that, to common observers, would 

 be pronounced to be the same, while their bite upon these very observers 

 would produce strikingly different effects. One is harmless, the other 

 deadly poisonous. The illustration, however, does not end here. The 

 poisonous nature of one of the reptiles is proved only so far as experiment 

 has been tried ; for while there is the above difference between them in 

 regard to their effects upon man, their bite may be in no wise different in 

 its effects upon swine. It is even possible that the harmless and poisonous 

 natures may be exchanged in regard to some animals bitten by them. 

 Thus the question becomes a complicated one, and can only be settled by 

 having at command all the facts in the case. Even upon the same ani- 

 mals the effects may not always be the same, for the conditions of the 

 system change in such manner that disease is caused at one time, and at 

 another the influence is entirely thrown off. Now, knowing these and 

 similar things to be true of animals, does it not seem probable that like 

 complications may be found among plants? If it is admitted that much 

 close observation is necessary in order to arrive at truthful conclusions 

 among beings which are well known, and whose actions are easily seen, 

 what must follow as a necessity when we deal with comparatively unknown 

 forms, whose workings are in secret, and of whose mysterious energies we 

 know little or nothing ? Is it a wonder that men should have disagreed 

 about the habits and influences of living structures, too small to be seen 

 at all by the unaided vision, and too subtle in their operations to be dis- 

 covered except by skillful and laborious research ? Such, however, are 

 the most of the parisitic fungi. Thousands of these minute forms find 

 lodgment upon a single leaf, yet their presence is unsuspected by the cul- 

 tivator, who wonders and worries over the sickly condition of his plants. 

 By the aid of the microscope they may be seen and studied, but no one 

 sees them bite, neither are poison sacks found at the base of horrid teeth, 

 by which the mischief is accomplished. It is therefore necessary to 

 patiently watch the effects of their growth in the special case at hand, as 

 well as to know, as fully as possible, the general conditions and require- 

 ments of both the healthy and diseased states of all the organisms under 

 consideration. 



Now, in a general way, it is well known that the conditions of 

 growth are very different between fungous and other plants. They seem 

 to be the opposites of each other. With rare exceptions, all other plants 

 are dependent upon light for their existence. Deprived of sunlight, they 

 speedily perish. The potato, stored as it is with prepared material, sprouts 

 in the cellar, but only attains a feeble, useless development, adding noth- 

 ing to its substance. House plants, provided with the best soil, and 

 receiving the best attention in other respects, fail utterly with the window 



