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ments of plant food. Such an experiment is interesting as show- 

 ing how quickly the healthiest organism can fall a prey to disease 

 and become dilapidated. 



The explanation of the appearance of some of our most trouble- 

 some diseases affecting plants at the present time can be found in 

 part in the practice of increased forcing, and is also due to the fact 

 that new parasitic organisms have been introduced from time to 

 time from other countries through traffic. Some of these fungi, 

 however, which have recently proven disastrous, have been with us 

 for some years, if not always, and the reason of their becoming 

 more troublesome at the present time can be attributed to the 

 increased production of more succulent, tender plants, brought 

 about by forcing, which enables these parasites to find more favor- 

 able conditions in which to thrive. AVith every modification aud 

 innovation in the growing of plants, there is likely to occur new 

 difficulties and obstacles to overcome. 



Constitutional weaknesses which develop in some varieties and 

 are inherited in others are unfavorable to immunity. Varieties 

 of carnations inclined to succulency, or containing two or three 

 per cent more water contents in their leaves, have proven much 

 more susceptible to rust than those containing less water. 



There is little doubt but that many diseases could be prevented 

 by modifications in the methods of growing plants, if such could 

 be adopted. The so-called "drop" in lettuce would prove less 

 disastrous if the plants could be elevated from the soil sufficiently 

 to allow air aud light to penetrate to the stem. This would result 

 in producing firmer and more resistant tissues. 



Experiments have shown that a covering of coarse sand about 

 lettuce plants materially reduced rots, simply from the fact that 

 sand retains moisture much less readily than loam, thus offering 

 less favorable opportunities for fungous infection, and no doubt a 

 circulation of air about the stems would prove beneficial. In the 

 same manner, subirrigation reduces stem rots by maintaining a 

 smaller amount of moisture in the top layers of soil. The shutting 

 out of light and air by planting too thickly constitutes a source of 

 danger to disease. Water cress and parsley offer good examples 

 of the effects of overcrowding, due to luxuriant growth. When 

 these crops are allowed to grow high and become thick they pro- 

 duce weak stems, and become affected with the same fungus that 

 produces "drop" in lettuce, whereas when closely cropped there 

 is little loss from this disease. The exclusion of light and air 

 necessarily arising from overcrowding are responsible for this. In 

 most instances the stem rots of the chrysanthemums have been 



