98 THE UNHEATED GREENHOUSE 



early flowering, and later be removed to the greenhouse, 

 where the spikes of pure white flowers will be very acceptable. 

 There are many garden forms, single and double, of this Bell- 

 flower, of which the type is blue, but a very good one for the 

 purpose in view is that known as the large white Cambridge 

 variety. 



The preparatory process thus sketched will be found useful 

 for other herbaceous plants, and may be tried with modifica- 

 tions for any perennial which seems in the grower's fancy to 

 be suitable and desirable. Heuchera sanguinea with its 

 spikes of carmine-red, Tiarella cordifolia, the feathery white 

 plumes of which are never out of place, though never so 

 lovely as in their native woods, the long-spurred Rocky 

 Mountain Columbines (Aquilegia ccerulea and A. chrysantha) 

 are all wild flowers of the New World, well known now in our 

 best gardens, but they may be pressed into the service of the 

 cold greenhouse should circumstances suggest their use. It 

 is a well-known fact that plants can be educated, so to speak, 

 to change their time of flowering. A species, for example, 

 which flowers naturally in June, by an alteration of treatment 

 and temperature may be induced to bloom in April. The 

 following season, in all probability, with the same treatment, 

 the flowers will appear a month earlier, until, instead of 

 midsummer, that particular specimen gradually becomes 

 accustomed to open its flowers in spring. This tendency to 

 change of habit is a very useful one, and should be turned 

 to the best advantage by the cold-house gardener. 



Primroses of several different types are valuable in the 

 earlier months of the year, and follow each other in obliging 

 succession. Dean's hybrid forms of the common Primrose 

 (P. acaulis) make pretty groups of many shades pure white, 

 lilac, and deep crimson being found amongst them, as well as 

 the normal Primrose colour. In arranging these in a green- 

 house it is well to group them in gradations of one colour, 



