396 



ODOUES OF FLOWEES. 



lacese and Oonvolvulacese, red ; Campanulacese, blue ; Eartunculaceae, 

 yellow. 



In arranging flowers in a garden it is of importance to place the 

 complementary colours together, in order to produce the best efieot. 

 The complementary colour of red, or that which is required to make 

 white light, is green ; of orange, blue ; of yellow, violet ; consequently 

 blue and orange-coloured flowers, yellow and violet, may be placed 

 together ; while red and rose-coloured flowers harmonise well with 

 their own green leaves. When the colours do not harmonise, the 

 interposition of white or of black often restores harmony. 



5. — Odours of Flowers. 



The peculiar odours of plants depend on various secreted volatile 

 matters, which are often so subtle as to be incapable of detection by 

 ordinary chemical means. Nothing is known of the causes which 

 render one flower odoriferous and another scentless. In some cases 

 the odours of plants remain after being dried, but in general they 

 disappear. Some leaves, as of the Woodruff, become scented only 

 after drying ; and certain woods, as Teneriffe rosewood, give out their 

 odour only when heated by friction. Meteorological causes have a 

 great influence on the odours of living plants. Dew, or gentle rain 

 with intervals of sunshine, seem to be the circumstances best fitted 

 for eliciting vegetable perfumes. Light has a powerful effect on the 

 odour as well as the colour of flowers. Plants, when etiolated by 

 being kept in darkness, generally lose their odour. In certain cases 

 the perfumes of flowers are developed in the evening. Some of these 

 plants were called tristes by Linnseus, as Hesperis tristis, or night- 

 scented stock. Many orchidaceous plants are fragrant at night only, 

 as some Catasetums and Cymbidiums. Oestrum noctm-num and the 

 white flowers of Lychnis vespertina are also night-scented. The odours 

 of some plants are peculiarly offensive. This is the case with Phallus 

 impudicus, and with the flowers of many Stapelias. 



Schubler and Kohler, whose investigations in regard to colour have 

 been noticed, have also made observations on the odours of plants in 

 the same monocotyledonous and dicotyledonous orders. The following 

 tables show some of their results : — 



