CULTIVATJON. 335 



In the latter case, somebimes their own weiglit makes 

 them fall lower than is convenient-; it therefore 

 becomes necessary to support them by inconspicuous 

 stakes. Care must, however, be taken not to raise the 

 fronds above their natural position, ani to avoid making 

 them have a stiff formal appearance. 



In " Theories of Horticulture," it is said that 

 abundance of hght and a free circulation of air are 

 indispensable for the cultivation of plants under glass. 

 In my long experience, I have found, as a rule an 

 abundance of light and a too free circulation of air 

 prejudicial to the good cultivation of plants in general. 

 With regard to Perns, they love a quiet, dull atmo- 

 sphere ; the light afforded by a roof glazed with the 

 ordinary transparent glass, admits fally double the 

 amount of light necessary during eight months of the 

 year. Sufficient means are, however, necessary for 

 admitting air, in order to keep down the temperature 

 in summer ; but care must be observed in admitting 

 it ; if not, the increased ventilation in lowering the 

 temperature will cause a rapid dispersion of the essen- 

 tial moist atmosphere at a time when most required. 

 Shading must then be resorted to, this being the chief 

 purpose which it serves, besides protecting the plant's 

 foliage from the too powerful rays of the sun. It may 

 consist of canvas blinds on rollers; two moderately 

 thick ones are much better than one very thick, espe- 

 cially when Tnchomanes and Hymenophyllum are 

 grown ; one should be permanent during the height of 

 the summer, the other to roll over it on occasions of full 

 sunshine. Although canvas is here spoken of as best 

 for shading, and is extensively used, still it is trouble- 

 some, and in the end expensive, which makes it de- 



