GREENHOUSE AND CONSERVATORY. 



523 



pest. For cultivation in pots, young plants 

 should be potted singly in 60's, or four plants 

 in 32's. Violets may be advantageously grown 

 in the open on raised beds, shaped in the form 

 of a steep ridge, and planted on both sides. 

 They are sometimes attacked by a fungoid 

 disease which causes dry, whitish spots on the 

 leaves, often proving troublesome when the 

 plants are grown under glass. Mr. Massee 

 recommends spraying with dilute Bordeaux 

 mixture as a cure. Badly infested plants 

 should be burnt. Cuttings should be taken 

 only from perfectly healthy plants. 



Select Varieties. 

 Double. 



Marie Louise. Excellent for autumn and winter 

 blooming. Large, rich lavender-blue. 



Lady Hume Campbell. Later, and a shade darker 

 than Marie Louise. 



Neapolitan. Lavender, with white eye. One of the 

 best and largest ; later, and not so free as either of the 

 above. 



Be Panne, pale violet; early, very free. 



Sivanley White. A grand companion to Marie Louise ; 

 very free. 



Single. 



Wellsiana. Perhaps the finest single ; dark, very large. 

 Victoria Regina. Fine flowers with long stalks. 

 The Czar. Very dark and free. 



Princess of Wales. Very large, free; bright in colour. 

 Double Russian. Invaluable for its extreme lateness. 

 La France. Very large, stiff -stalked ; bright blue-purple. 



[J. S.] 



CHAPTER XXVIII. 



GREENHOUSE AND CONSERVATORY. 



I. The Greenhouse. 



A greenhouse is a glass -roofed structure 

 devoted to the cultivation of plants that re- 

 quire protection from extremes of weather. 

 In England the term is limited by gardeners 

 to houses in which the temperature is regu- 

 lated by means of ventilators and shading, 

 except in cold weather, when artificial heat 

 is employed to keep up a temperature a few 

 degrees above freezing-point. The plants 

 usually grown in such a house are known as 

 greenhouse plants, as distinguished from stove 

 plants, &c. A popular classification of indoor 

 plants, according with their grouping for con- 

 venience of cultivation, is: — (1) Stove Plants, 

 (2) Greenhouse Plants, (3) Stove Ferns, (4) 

 Greenhouse Ferns, (5) Stove Orchids, (6) 

 Greenhouse or Cool Orchids. Using the term 

 Greenhouse as here defined, it is limited to a 



structure devoted to such plants as Pelar- 

 goniums, Fuchsias, Camellias, Cape Heaths, 

 Bouvardias, Boronias, &c. As a rule they are 

 plants that thrive only when provided with 

 all the light possible, except when there is 

 danger of sun-scorching. 



The necessity of light to vegetable life is 

 better understood at the present day than in 

 times past, particularly as regards the plants 

 we grow under glass, and more especially such 

 as require greenhouse treatment, which in 

 most cases are indigenous to countries where 

 the light is much in excess of that which our 

 climate affords, even in the open air. There 

 is undoubtedly in plants a certain ability to 

 adapt themselves to circumstances of situation 

 very different from those under which the indi- 

 vidual species or variety existed in a state of 

 nature; otherwise, the majority of the plants 

 we cultivate under glass would fail Yet there 

 are some elements so indispensable to the 

 existence of many of them, that even after a 

 lengthy period of existence under artificial 

 treatment, during which they have been inured 

 to altered conditions, they are still as unable 

 to dispense with them as they were the day 

 they left their native country. Amongst these 

 light is of the first importance. A plant that 

 in its native habitat is fully exposed to unob- 

 structed light cannot as a rule be grown arti- 

 ficially unless allowed plenty of light by the 

 cultivator. 



Span-roofed greenhouses are by far the best 

 for general purposes. Their height must be in a 

 measure determined by their width. In houses 

 devoted to the growth of greenhouse plants 

 there is little internal moisture, consequently 

 there is not likely to be much drip through 

 condensation of vapour upon the glass and 

 sash-bars, which is often troublesome in houses 

 where there is much moisture, unless the roof 

 has sufficient pitch to cause the water so con- 

 densed to run down the bars. For greenhouses 

 we prefer a roof-angle of 40°. 



In all cases these span-roofed plant structures 

 should stand at right angles to the south, by 

 which means all the light during the best part 

 of the day is available, whereas if they stand 

 in the opposite direction- — that is, at right 

 angles to the west — the plants are in shadow 

 during the greater part of the day in winter, 

 when they require all the light possible. 



In addition to the side-lights being made to 

 open, it is necessary to have ample means for 

 roof ventilation. To secure this there are many 

 contrivances, some of them very complicated 



