2 THE UNHEATED GREENHOUSE 



standing of what is meant by a cold greenhouse. It is one in 

 which it is neither convenient nor desirable to have a fixed 

 heating apparatus, and in which it is only intended to prevent 

 the temperature from falling below 35 or, in other words, 

 simply to keep out frost. The term " fixed " is used 

 advisedly, for though there may be cases of glass corridors or 

 of a larger glass-garden in which an ordinary fixed flow-and- 

 return pipe might answer better than a removable apparatus, 

 it must be borne in mind that the main principle of the 

 unheated greenhouse except during the few dead and dark 

 weeks which precede and follow the shortest day, or on the 

 occasion of a sudden fall of temperature or of damping fog 

 is to keep it cool enough for the plants of temperate regions, 

 which alone are suitable to be grown in it. It goes without 

 saying that the mere shelter of glass will not keep out severe 

 frost. Therefore some means of raising the temperature 

 under certain conditions of weather, to be considered later, 

 are not forbidden to the cold greenhouse; but artificial 

 heat being, in a general way, not only needless but undesir- 

 able, it should be on all accounts as temporary in its character 

 as possible. Heating power of even the most temporary 

 character may be entirely dispensed with, as in the case of an 

 alpinery, which is one of the most delightful forms of the cold 

 greenhouse, but, of necessity, it limits in some degree the 

 choice of plants. 



It must be confessed that such unheated glass-houses are by 

 no means in favour. The professional gardener, as a rule, 

 pins his faith to the boiler and pipes, and looks askance at 

 the plants which will thrive in a temperature lower than from 

 60 to 80. Tinctured with the hurry and impatience of 

 slow results characteristic of the age, he rejoices in the quick 

 development of fine showy plants, and it is not to be denied 

 that splendid success follows his skilful culture. Much of the 

 success is ephemeral, however, not to say stereotyped. One 



