TROPICAL AND TEMPERATE HOUSES. 75 



and the north side with glass, a plan which 

 admits abundance of light, and renders shading 

 wholly unnecessary. The whole structure is 

 placed on a slope, the lower part being consid- 

 erably below the outside ground-level. At this 

 lowest part is placed the furnace, and there is an 

 extra service of pipes there to maintain a stove 

 temperature. At the upper end, the pipes suffice 

 only to keep frost out. Thus in one house the 

 ferns of tropical, temperate, and frigid zones are 

 all accommodated ; and though the whole structure 

 is rough, and has been constructed on the most 

 economical principles, the interior presents at all 

 seasons a grand spectacle, and affords a most de- 

 lightful promenade." Fern Garden, pp. 98, 99. 



Of course, to grow to perfection any of the taller 

 species of arborescent ferns, a very high roof, or a 

 dome on some portion of the structure, will be re- 

 quired. Alsophila excelsa at the Botanic Garden, 

 Cambridge, Mass., has now reached the glass at 

 the highest part of the house, some twenty-five 

 feet above the floor. This plant is many years old. 



Our greenhouses are usually built in summer ; 

 and, for this reason, there is danger of our uncon- 

 sciously making them too weak to endure the 

 strain of ice and heavy snows which the winter of 

 our rigorous Northern climate will bring. Between 

 May and October, it is very hard to realize that 

 those charming designs contained in the English 



