ii 



CASSELL'S POPULAR GAEDENINa. 



then Trat very imperfectly realised ; it can hardly he 

 said to be yet perfectly understood. Any glass, the 

 thicker the better, was gladly welcomed hy the cul- 

 tivator to protect his plants from the injurious 

 and destructive influences of cold. As these 

 plants were from the necessity of the case generally 

 or invariably in the open ground, it followed that 

 the glass had to be carried to the plants — ^not the 

 plants to the glass, as is now so generally done. 



Hence the origin of bell-glasses, hand-lights, glass 

 boxes, frames, and all the smaller glass protectors and 

 appliances now so common and so useful in horti- 

 cultural practices. They carried protection to the 



unless unusuaUy well made, mostly admits more or 

 less of the surrounding air to the atmosphere it 

 encloses. Hence, for purposes of propagation, i- 

 whioh the production and maintenance of a semi- 

 saturated atmosphere is indispensable, beU-glasses 

 are best ; while for the mere purposes of protection, 

 hand-lights are generally equally good, and even 

 in more general use. 



However, the distinction here made between beU- 

 glasses and hand-lights is not always found to exist 

 in practice, for though beU-glaises as a rule are 

 mostly cut or moulded in one piece, considerable in- 

 genuity and expense have been expended on them to 



Vig. 1.— MovaWe Top. 



Fig. 2.— With Knob. 

 BELL-GI.ASSES. 



Fig. 3.— Without Knob. 



plants, and enabled them to bridge over climatic 

 severities in safety, thus earning the well-merited 

 description of portable green-houses and conserva- 

 tories in miniature ; and they are such, if function 

 rather than area is to be accepted as the basis of our 

 descriptive names. Hence it may prove as logical 

 as convenient to begin our notes on green-houses and 

 conservatories with these more humble glass struc- 

 tures and appliances. 



Bell-glasses. — Horticultural history is silent 

 on the point of whether the bell-glass or the 

 hand-light was the first in the field as a plant pro- 

 tector. Most probably the former. The most vital 

 difference between them is that the one is run or 

 moulded in one piece ; the other is formed or made 

 of several. This is not a mere distinction without a 

 difEerence. The beU-glass seals the enclosed atmos- 

 phere hermetically, cutting ofi all contact with the 

 external air. The hand-glass, on the contrary. 



make the top movable at wiU (see Fig. 1) for pur- 

 poses of ventilation and the moderating of extremes 

 of temperature. By removing the super glass 

 that seals the opening in the crown, the enclosed 

 temperature can be adjusted to a nicety and any 

 amount of air admitted. This obviates the necessity 

 of moving the glass bodily, which is objectionable on 

 the ground of inconvenience in the case of larjje 

 glasses, and also because, when frequently moved, 

 the glass seldom sits so closely on its base as to 

 render it whoUy air-proof at that point, a mattei 

 of more importajace in propagation than for protec- 

 tive purposes. 



The major portion of bell-glasses have, however, 

 always been, and are still, made in one piece, and 

 hence, if placed on an even and level base, hermeti- 

 cally seal the enclosed area. They are made of dif- 

 ferent sizes, from two inches to twelve inches of 

 more in diameter. They may also be had with o* 

 without knobs (see Figs. 2 and 3). We had almost 



