92 INTRODUCTION 



that are regarded as having been derived from ammonia, hydrogen atoms of this 

 being replaced by an alcohol radical. The best known odour belonging to this 

 group is that of the hawthorn (Crataegus Oxyacantha and monogyna) which 

 suggests the smell of herring brine, and is due to trimethylamine. As Kerner 

 mentions, the odour of hawthorn is found with slight variations in the flowers of the 

 pear (Pyrus communis), medlar (Mespilus gerraanica), rowan (Sorbus Aucuparia), 

 many meadow-sweets (e.g. Spiraea ulmifolia, chamaedryfolia), guelder-rose and way- 

 faring-tree (Viburnum Opulus and Lantana), chestnut (Castanea vesca), racemose 

 elder (Sambucus racemosa), wild clematis (Clematis vitalba), and barberry (Berberis 

 vulgaris). Similar also is the odour of horse-chestnut (Aesculus Hippocastanum), 

 manna-ash (Fraxinus Ornus), ivy (Hedera Helix), and others. I may here at once 

 point out a peculiarity that is common to most of the flowers just mentioned, i.e. that 

 they conceal their honey very superficially, so that it is accessible to insects with the 

 shortest proboscis. In fact such insects, especially flies (Muscidae), are particularly 

 conspicuous as visitors of these flowers. 



3. Benzoloid Odours. These are odours that are peculiar to the derivatives 

 of benzol, in which the hydrogen atoms of a benzol nucleus are replaced by alcohol 

 or acid radicals. Kerner assigns to this group the odour, due to engenol, of several 

 carnations (Dianthus Caryophyllus, plumarius, superbus), also the odour of hyacinths 

 (derived from cinnamyl-alcohol), the odour of Spiraea Ulmaria (derived from salicyl 

 aldehyde), the cumarin-odour of woodruff, and the vanilla-odour of heliotrope ; and 

 beside these the respective odours of lilac (Syringa vulgaris), lily of the valley 

 (Convallaria majalis), mignonette (Reseda odorata), jessamine (Jasminum officinale), 

 auricula (Primula Auricula), honeysuckle (Lonicera Caprifohum), false acacia 

 (Robinia Pseudacacia), violet (Viola odorata), sow-bread (Cyclamen europaeum), 

 Paulownia (P. imperialis), and Ylang-ylang (Unona odoraiissima), to which may 

 be added the plum-like odour of Muscari racemosum and Polygala Chamaebuxus. 



The varieties of benzoloid odour just named are repeated, with some modi- 

 fication, in many other flowers, a number of which are given by Kerner. The 

 following possess : — 



(a) Carnation-odour : Orobanche caryophyllacea, gracilis, lucorum ; Platanthera 

 bifolia, Gymnadenia conopsea, Ribes aureum, Narcissus poeticus ; 



(3) Hyacinth-odour : Silene nutans, longiflora, noctiflora ; Hesperis tristis ; 

 Pelargonium atrum, glauciifolium, and others; 



(f) Woodruff-odour : Anthoxanthum odoratum, Hierochloa odorata, species of 

 Melilotus (mixed in these last with the odour of honey); 



(d) Vanilla-odour : Heliotropium peruvianum and europaeum; Asperula glo- 

 merata, cynanchica, longiflora ; Linnaea borealis, Sambucus Ebulus, Convolvulus 

 arvensis, Gymnadenia odoratissima, Nigritella nigra, Saussurea alpina. Daphne 

 alpina, Epipogon aphyllum ; 



{e) Lilac-odour : Daphne striata and pontica. 



i^f) Lily-of-the-Valley-odour : Echinocactus Tetani; 



(^) Acacia-odour : Cytisus alpinus, Spartium junceum. Iris odoratissima; 



(h) Auricula-odour : Sp. of Primula, TroUius europaeus ; 



(;') Honeysuckle-odour : Nicotiana affinis ; 



