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CHAPTER IV. 
CULTIVATION IN WAEDIAN CASES AND 
GREENHOUSES. 
When first Mr. Ward introduced among us his most 
happy invention of glazed cases for growing ferns, he 
announced the reasons upon which he had based his 
theory for their construction. 
His first desideratum was protection from the smoke 
and dust with which the air of towns is laden, which 
smoke and dust adhere to the fronds of the ferns and 
obstruct their breathing-organs, as similar impediments 
affect the lungs of the human race. 
His second desideratum was protection from the ex- 
tremes of heat and cold. The experiments of Sir C. 
Blag den and others having demonstrated that both ani- 
mals and vegetables will endure without injury the 
extremes of heat and cold provided the atmosphere be 
undisturbed, the securing of an atmosphere of perfect 
stillness is equivalent to the securing one of more equal 
temperature. The validity of this argument in the 
matter in question is proved by the fact that the Hyme- 
nophyllums and Trichomanes have borne exposure to the 
sun, and Asplenium molle, Phoenix dactyliferus , and 
Dendrobium pulchellum have lived without heat, under 
the protection of the Wardian case. 
