FUNGOID PESTS OF CULTIVATED PLANTS. 7 



intervening period of rest. Thus much it seemed necessary to explain, 

 as it has some connection with the dispersion of the Uredines, and the 

 steps to be taken in contending with them. It will be evident at once 

 that the destruction of these clusters of teleutospores will minimise the 

 spring infections, and hence that they should be well looked after and 

 destroyed, either by effective fungicides, or by burning up all the dead 

 leaves and stems of the foster plants known to have been affected. In 

 this case, again, we must suggest the importance of acquiring some 

 practical knowledge of the history and mystery of such plant parasites, 

 if they are to be encountered and vanquished in their career of de- 

 struction.. 



In this connection we cannot omit alluding to the evidence, which 

 is gradually accumulating, of the connection between those minute 

 organisms the microbes, or Schizomycetes, and plant diseases. There 

 are certain diseases which attack cultivated plants, and produce disastrous 

 results which have long been a mystery, since, although the host-plants 

 appeared to be suffering from the attacks of some insidious fungus 

 disease, none of the usual external appearances could be detected. In 

 several cases of this kind it has been affirmed, although not yet com- 

 pletely confirmed, that the disease is caused by the presence of a minute 

 bacterium or bacillus in immense numbers. There is no reason ana- 

 logically why this should not be the case, and all the evidence seems to 

 strengthen the probability ; but the suggestion is so recent and the inves- 

 tigation so difficult that it would be imprudent to hazard any very decided 

 opinion. Researches into a Vine disease in California, a Melon disease in 

 some parts of the United States, and the very prevalent " Peach yellows " 

 almost establish the fact that microbes are present in large numbers, and 

 are hypothetically the cause of the disease. In reference to the disease 

 of Cucumbers and Melons it has been claimed that the disease is accom- 

 panied profusely by bacteria ; that the juice of diseased plants swarming 

 with these organisms, when transferred to healthy plants, will inoculate 

 them with the disease, which will make its appearance in three or four 

 days ; that seed watered with the juice of diseased fruits did not 

 germinate, or only 25 per cent, germinated at all, and these soon decayed ; 

 that the diseased juice when introduced into healthy stems and fruits of 

 Tomato rapidly produced decay ; that young Tomato plants in proximity 

 with diseased Cucumbers were all destroyed. Hence it is concluded that 

 the disease in question is caused by bacteria, and may be transmitted to 

 other plants by inoculation. If all this should be confirmed, then we 

 shall have to deal w r ith another class of plant diseases, of fungoid origin, 

 which will require a different mode of treatment, and doubtless offer a 

 stubborn resistance. 



From the foregoing observations it will be manifest that there are 

 such broad distinctions between different groups of pestiferous fungi that 

 they should not all be subjected to the same mode of treatment, and 

 that the remedies which might be successful in cases of one kind would 

 be powerless in another. Hence, then, modes of treatment must have a 

 relation to the known character of the parasite. It follows from this 

 that a certain amount of knowledge of the life-history and affinities of 

 the parasite must precede any definite effort to counteract or destroy it, 



