98 FERNS IN THEIR HOMES AND OURS. 



large slug to have his own way, rather than disturb the shade 

 when the case was looking finely ; and, in many instances, 

 have allowed decayed fronds to remain, rather than run the 

 risk of destroying the arrangement by removing the shade. 

 It was almost as much on this account as for ventilation 

 that I constructed the dome-top or ventilated fern-case, which 

 is as easily managed as an ordinary Wardian-case. Lifting 

 the dome does not disarrange the plants, as they are all con- 

 fined within the cylinder, which need never be disturbed for 

 this purpose. This case is constructed as follows : — 



" The case or stand is of wood, six inches deep, and rest- 

 ing upon three small feet. There is a large opening under- 

 neath, covered with a movable slide to admit or exclude the 

 air. It has a zinc pan one-half an inch less all round than 

 the wooden case. This half-inch space is covered all around 

 at the top of the pan, which leaves a flat surface of zinc one 

 inch wide, with an outside rim to receive the glass cylinder. 

 This flat surface of zinc is pierced with half-inch holes in its 

 entire circumference about three inches apart. When the 

 glass cylinder is in place, the half-inch holes are inside 

 the case. The cylinder, of annealed glass, fits neatly into the 

 zinc rim, and is fifteen inches in diameter by fourteen inches 

 in height. Encircling the upper edge of the cylinder is a 

 copper rim, one inch wide, with edge turned downward on 

 the outside, a quarter of an inch wide, to fit on to the cylinder. 

 The flat surface of the rim is perforated with quarter-inch 

 holes ; and the inner edge turns up a quarter of an inch to 

 receive the dome, or cover, which is eight inches high, and 

 twelve and a half inches in diameter. The holes in this cop- 

 per rim are on the outside ; so that, when the valve in the bot- 

 tom of the case is open, the air passes up through the holes 

 round the zinc pan, and out at the copper rim. The whole 

 case, when complete, stands twenty-nine inches high." 



The ventilation of the circular fernery is more 



