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tained. From this it is evident that leaf mould, an extremely favorable sub- 

 stratum for most other plants and in which the orchids named at first grow 

 very well, gradually becomes slimy when copiously watered (especially with 

 water containing algae) and does not let the necessary supply of oxygen 

 reach the roots of the orchids. 



Much better results have been obtained with the so-called Jadoo fibre, 

 a very porous moss peat saturated with nutritive salts. Yet the result does 

 not justify the increased expense and the old sphagnum culture always 

 proves to be the most advantageous. The modern endeavor of growers to 

 force the orchids to an earlier and more luxuriant development by abundant- 

 ly supplying nutritive substances, high temperatures and great moisture, 

 gives actual good results only for a Hmited time. Usually a reaction sets in 

 in the over-stimulated plants, which can be prevented only by a dormant 

 period in a relatively cooler, drier place. 



Cooler, drier sand is also in many cases the best protection against decay 

 from fungus. Klitzing observed a very instructive example in a spot dis- 

 ease of Vanda coerulea, called forth by Gloeosporium which is now pretty 

 universal on the continent and in England, as well as even in our country. The 

 statements of the collectors show that this Vanda is found in the Himalayas 

 on Gordonia, which grows in moderately warm, windy habitats. Here, in 

 our conservatories, the plants are cultivated, on an average, more than 10° C. 

 warmer and kept year in and year out in closed, moist greenhouse air. Nat- 

 urally the plants become more tender on this account and succumb within a 

 few days when artificially infected with Gloeosporium, while, in their native 

 habitat, the fungus is restricted and the plants develop further and increase, 

 despite its presence. 



