THE WELCOME OF THE FLOWERS 



401 



veins on a greenish or fawn-coloured background." 

 belong those 



and red-brown 

 the aminoid group 

 volatile substances which diffuse 

 into the air and have an amine as 

 their foundation, like the scents of 

 Hawthorn, Ivy, and Mountain Ash. 

 The benzoloid group comprises those 

 scents which are formed from the 

 so-called aromatic bodies, like oil of 

 cloves and vanilla, and are found in 

 the Honeysuckle, Wallflower, Pink, 

 Violet, Lilac, and a host of other 

 flowers. The paraffinoid scents 

 include the vegetable acids and 

 alcohol of those hydrocarbons which 

 are known as paraffins, such as 

 valerian ic acid and oil of rue. 

 They are found in the Rose, Vale- 

 rian, Rue, Elder, etc. The last or 

 terpenoid group consists of scents 

 produced from ethereal oils destitute 

 of oxygen, called terpenes ; the 

 well-known oil of lavender is one of 

 them. They are usually developed 

 in the tissues of the stems and 

 foliage, but the Citron, Lavender, 

 Thyme, Magnolia, and some other 

 plants produce them in their flowers. 

 Many flowers which are not 

 cross-pollinated by insects, and some 

 few that are, are quite odourless to 

 man ; though it does not follow of 

 necessity that they are scentless to 

 insects. To take an example : The 

 flowers of the Virginia Creeper 

 (Ampelopsis quinquefolia), in which 

 we oan detect no scent, evidently 

 appeal to the olfactory sense of 

 bees ; otherwise it would be im- 

 possible to account for the readiness 

 with which they find out the flowers, 

 which have green corollas and are 

 undistinguishable among the leaves 

 at a little distance. As an instance 

 ii 8 



To 



Photo by] [E. Step. 



FIG. 496. TWAYBLADE (Listen ovata). 



An Orchid with very small flowers, but each flower with 



remarkable arrangements to ensure cross -pollination. 



